109464: server: batch large span stats requests r=zachlite a=zachlite

Previously, span stats requests could only request a maximum of 500 spans at a time, otherwise the request would return an error.

This commit adds transparent batching at both the system tenant's handler and the secondary tenant's handler. The cluster setting `server.span_stats.span_batch_limit` is used to control the size of the batches. The default value has been raised to 1000.

Resolves #105638
Epic: CRDB-30635
Release note (ops change): Requests for database details or table details from the UI, or usages of `SHOW RANGES WITH DETAILS` are no longer subject to errors if the number of requested spans is too large.

109612: serverutils: implement the testserver interfaces indirectly r=stevendanna a=knz

First commit from #109591.
Epic: CRDB-18499
Fixes #107058.

TLDR: unit tests using TestServer/TestCluster now produce warning and
notice messages upon certain suspicious API usage.

For example:
```
$ dev test //pkg/server/storage_api -f TestStatusGetFiles
=== RUN   TestStatusGetFiles
    ...
        pkg/server/storage_api/storage_api_test_test/pkg/server/storage_api/files_test.go:46: (TestStatusGetFiles)
                NOTICE: .GetStatusClient() called via implicit interface ApplicationLayerInterface;
        HINT: consider using .ApplicationLayer().GetStatusClient() instead.
    conditional_wrap.go:193: TIP: consider replacing the test server initialization from:

            ts, db, kvDB := serverutils.StartServer(t, ...)
            // or:
            tc := serverutils.StartCluster(t, ...)
            ts := tc.Server(0)

        To:

            srv, db, kvDB := serverutils.StartServer(t, ...)
            defer srv.Stop(...)
            ts := srv.ApplicationLayer()
            // or:
            tc := serverutils.StartCluster(t, ...)
            ts := tc.Server(0).ApplicationLayer()
```

The following warnings/notices are implemented.

**ApplicationLayerInterface**

The problem here is that the implicit implementation of
`ApplicationLayerInterface` inside `TestServerInterface` is likely
misused. If/when the test server automatically starts a secondary
tenant, the *implicit* `ApplicationLayerInterface` refers to the
system tenant, whereas only `.ApplicationLayer()` refers to the
secondary tenant. It's likely that the test code should use the
latter.

For this, a warning is printed when a method from the *implicit*
`ApplicationLayerInterface` is called.

The warning is not printed if the test has indicated (via
`DefaultTestTenant: base.TestIsForStorageLayerAndNeedsASystemTenant`)
that it is ever only interested in the storage layer.

**StorageLayerInterface**

We want to promote the use of the explicit interface accessor
`.StorageLayer()` to access the methods of `StorageLayerInterface`.

For this, a notice is printed when a method from the *implicit*
`StorageLayerInterface` is called.

The notice is not printed if the test has indicated (via
`DefaultTestTenant: base.TestIsForStorageLayerAndNeedsASystemTenant`)
that it is ever only interested in the storage layer.

**TenantControlInterface**

We want to promote the use of the explicit interface accessor
`.TenantController()` to access the methods of
`TenantControlInterface`.

For this, a notice is printed when a method from the *implicit*
`TenantControlInterface` is called.



109863: roachtest: add npgsql tests to ignorelist; not blocklist r=rafiss a=rafiss

The previous commit 1928be2 accidentally put them in the wrong list. The blocklist is for tests that are expected to always fail, but a flaky test might pass sometimes.

fixes #109806
fixes #109738
Release note: None

109872: sql: coherent handling of hidden session vars in info_schema r=rafiss a=knz

Fixes #109870.
Epic: CRDB-28893

Release note (bug fix): Certain SQL session variables are meant
to be hidden from introspection but were showing up in
`information_schema.session_variables`, which was incoherent with the
handling in `pg_catalog.pg_settings`. This bug has now been fixed.

Co-authored-by: Zach Lite <zach@cockroachlabs.com>
Co-authored-by: Raphael 'kena' Poss <knz@thaumogen.net>
Co-authored-by: Rafi Shamim <rafi@cockroachlabs.com>