While working on #26751, I found that we are passing the container name on every single method although we don't need it as it is stored within the blobstore object already.

This PR simplifies a bit that part of the code.

While working on elastic#26751 and doing some manual integration testing I found that this elastic#22858 removed an important line of our code:

`AzureRepository` overrides default `initializeSnapshot` method which creates metadata files and do other stuff.

But with PR elastic#22858, I wrote:

```java
    @OverRide
    public void initializeSnapshot(SnapshotId snapshotId, List<IndexId> indices, MetaData clusterMetadata) {
        if (blobStore.doesContainerExist(blobStore.container()) == false) {
            throw new IllegalArgumentException("The bucket [" + blobStore.container() + "] does not exist. Please create it before " +
                " creating an azure snapshot repository backed by it.");
        }
    }
```

instead of

```java
    @OverRide
    public void initializeSnapshot(SnapshotId snapshotId, List<IndexId> indices, MetaData clusterMetadata) {
        if (blobStore.doesContainerExist(blobStore.container()) == false) {
            throw new IllegalArgumentException("The bucket [" + blobStore.container() + "] does not exist. Please create it before " +
                " creating an azure snapshot repository backed by it.");
        }
        super.initializeSnapshot(snapshotId, indices, clusterMetadata);
    }
```

As we never call `super.initializeSnapshot(...)` files are not created and we can't restore what we saved.

Closes elastic#26777.

While working on #26751 and doing some manual integration testing I found that this #22858 removed an important line of our code:

`AzureRepository` overrides default `initializeSnapshot` method which creates metadata files and do other stuff.

But with PR #22858, I wrote:

```java
    @OverRide
    public void initializeSnapshot(SnapshotId snapshotId, List<IndexId> indices, MetaData clusterMetadata) {
        if (blobStore.doesContainerExist(blobStore.container()) == false) {
            throw new IllegalArgumentException("The bucket [" + blobStore.container() + "] does not exist. Please create it before " +
                " creating an azure snapshot repository backed by it.");
        }
    }
```

instead of

```java
    @OverRide
    public void initializeSnapshot(SnapshotId snapshotId, List<IndexId> indices, MetaData clusterMetadata) {
        if (blobStore.doesContainerExist(blobStore.container()) == false) {
            throw new IllegalArgumentException("The bucket [" + blobStore.container() + "] does not exist. Please create it before " +
                " creating an azure snapshot repository backed by it.");
        }
        super.initializeSnapshot(snapshotId, indices, clusterMetadata);
    }
```

As we never call `super.initializeSnapshot(...)` files are not created and we can't restore what we saved.

Closes #26777.

While working on #26751 and doing some manual integration testing I found that this #22858 removed an important line of our code:

`AzureRepository` overrides default `initializeSnapshot` method which creates metadata files and do other stuff.

But with PR #22858, I wrote:

```java
    @OverRide
    public void initializeSnapshot(SnapshotId snapshotId, List<IndexId> indices, MetaData clusterMetadata) {
        if (blobStore.doesContainerExist(blobStore.container()) == false) {
            throw new IllegalArgumentException("The bucket [" + blobStore.container() + "] does not exist. Please create it before " +
                " creating an azure snapshot repository backed by it.");
        }
    }
```

instead of

```java
    @OverRide
    public void initializeSnapshot(SnapshotId snapshotId, List<IndexId> indices, MetaData clusterMetadata) {
        if (blobStore.doesContainerExist(blobStore.container()) == false) {
            throw new IllegalArgumentException("The bucket [" + blobStore.container() + "] does not exist. Please create it before " +
                " creating an azure snapshot repository backed by it.");
        }
        super.initializeSnapshot(snapshotId, indices, clusterMetadata);
    }
```

As we never call `super.initializeSnapshot(...)` files are not created and we can't restore what we saved.

Closes #26777.

While working on #26751 and doing some manual integration testing I found that this #22858 removed an important line of our code:

`AzureRepository` overrides default `initializeSnapshot` method which creates metadata files and do other stuff.

But with PR #22858, I wrote:

```java
    @OverRide
    public void initializeSnapshot(SnapshotId snapshotId, List<IndexId> indices, MetaData clusterMetadata) {
        if (blobStore.doesContainerExist(blobStore.container()) == false) {
            throw new IllegalArgumentException("The bucket [" + blobStore.container() + "] does not exist. Please create it before " +
                " creating an azure snapshot repository backed by it.");
        }
    }
```

instead of

```java
    @OverRide
    public void initializeSnapshot(SnapshotId snapshotId, List<IndexId> indices, MetaData clusterMetadata) {
        if (blobStore.doesContainerExist(blobStore.container()) == false) {
            throw new IllegalArgumentException("The bucket [" + blobStore.container() + "] does not exist. Please create it before " +
                " creating an azure snapshot repository backed by it.");
        }
        super.initializeSnapshot(snapshotId, indices, clusterMetadata);
    }
```

As we never call `super.initializeSnapshot(...)` files are not created and we can't restore what we saved.

Closes #26777.

* Use Azure upload method instead of our own implementation

We are not following the Azure documentation about uploading blobs to Azure storage. https://docs.microsoft.com/en-us/azure/storage/blobs/storage-java-how-to-use-blob-storage#upload-a-blob-into-a-container

Instead we are using our own implementation which might cause some troubles and rarely some blobs can be not immediately commited just after we close the stream. Using the standard implementation provided by Azure team should allow us to benefit from all the magic Azure SDK team already wrote.

And well... Let's just read the doc!

* Adapt integration tests to secure settings

That was a missing part in #23405.

* Simplify all the integration tests and *extends ESBlobStoreRepositoryIntegTestCase tests

    * removes IT `testForbiddenContainerName()` as it is useless. The plugin does not create anymore the container but expects that the user has created it before registering the repository
   * merges 2 IT classes so all IT tests are ran from one single class
   * We don't remove/create anymore the container between each single test but only for the test suite

Backport of #26751 in 6.x branch

)

* Use Azure upload method instead of our own implementation

We are not following the Azure documentation about uploading blobs to Azure storage. https://docs.microsoft.com/en-us/azure/storage/blobs/storage-java-how-to-use-blob-storage#upload-a-blob-into-a-container

Instead we are using our own implementation which might cause some troubles and rarely some blobs can be not immediately commited just after we close the stream. Using the standard implementation provided by Azure team should allow us to benefit from all the magic Azure SDK team already wrote.

And well... Let's just read the doc!

* Adapt integration tests to secure settings

That was a missing part in elastic#23405.

* Simplify all the integration tests and *extends ESBlobStoreRepositoryIntegTestCase tests

    * removes IT `testForbiddenContainerName()` as it is useless. The plugin does not create anymore the container but expects that the user has created it before registering the repository
   * merges 2 IT classes so all IT tests are ran from one single class
   * We don't remove/create anymore the container between each single test but only for the test suite

Backport of elastic#26751 in 6.0 branch

)

* Use Azure upload method instead of our own implementation

We are not following the Azure documentation about uploading blobs to Azure storage. https://docs.microsoft.com/en-us/azure/storage/blobs/storage-java-how-to-use-blob-storage#upload-a-blob-into-a-container

Instead we are using our own implementation which might cause some troubles and rarely some blobs can be not immediately commited just after we close the stream. Using the standard implementation provided by Azure team should allow us to benefit from all the magic Azure SDK team already wrote.

And well... Let's just read the doc!

* Adapt integration tests
* Simplify all the integration tests and extends ESBlobStoreRepositoryIntegTestCase tests

    * removes IT `testForbiddenContainerName()` as it is useless. The plugin does not create anymore the container but expects that the user has created it before registering the repository
   * merges 2 IT classes so all IT tests are ran from one single class
   * We don't remove/create anymore the container between each single test but only for the test suite

Backport of elastic#26751 in 5.6 branch

…26839)

* Use Azure upload method instead of our own implementation

We are not following the Azure documentation about uploading blobs to Azure storage. https://docs.microsoft.com/en-us/azure/storage/blobs/storage-java-how-to-use-blob-storage#upload-a-blob-into-a-container

Instead we are using our own implementation which might cause some troubles and rarely some blobs can be not immediately commited just after we close the stream. Using the standard implementation provided by Azure team should allow us to benefit from all the magic Azure SDK team already wrote.

And well... Let's just read the doc!

* Adapt integration tests
* Simplify all the integration tests and extends ESBlobStoreRepositoryIntegTestCase tests

    * removes IT `testForbiddenContainerName()` as it is useless. The plugin does not create anymore the container but expects that the user has created it before registering the repository
   * merges 2 IT classes so all IT tests are ran from one single class
   * We don't remove/create anymore the container between each single test but only for the test suite

Backport of #26751 in 5.6 branch

While working on #26751, I found that we are passing the container name on every single method although we don't need it as it is stored within the blobstore object already.

This commit simplifies a bit that part of the code.

It also removes `repositoryName` from AzureBlobStore which was not used anymore.
Also we move some properties in AzureBlobContainer to `private` members.

While working on #26751, I found that we are passing the container name on every single method although we don't need it as it is stored within the blobstore object already.

This commit simplifies a bit that part of the code.

It also removes `repositoryName` from AzureBlobStore which was not used anymore.
Also we move some properties in AzureBlobContainer to `private` members.

Backport of #26752 in 6.x branch