Description
This PR is to support below features for local context:

• change local context to global user level
• divide different default value source in help message
• add warning message when local context is on and take effect in current command
• add show/delete command for az local-context
• add LocalContextScenarioTest class in testsdk. All test cases for local context should extend it and it will do turn on/off work automatically.

Testing Guide
az local-context on

Command group 'local-context' is experimental and not covered by customer support. Please use with discretion.
Local context is turned on, you can run az local-context off to turn it off.

az group create -g myGroup -l eastasia

Local context is turned on. Its information is saved in working directory D:\code\cli. You can run az local-context off to turn it off.
Command argument values saved to local context: --name: xxj1
{
"id": "/subscriptions/0b1f6471-1bf0-4dda-aec3-cb9272f09590/resourceGroups/myGroup ",
"location": "eastasia",
"managedBy": null,
"name": "myGroup ",
"properties": {
"provisioningState": "Succeeded"
},
"tags": {
"StorageType": "Standard_LRS",
"type": "test"
},
"type": "Microsoft.Resources/resourceGroups"
}

az network vnet create -n myVNet --subnet-name mySubnet

Local context is turned on. Its information is saved in working directory D:\code\cli. You can run az local-context off to turn it off.
Command argument values from local context: --resource-group: xxj1
Local context is turned on. Its information is saved in working directory D:\code\cli. You can run az local-context off to turn it off.
Command argument values saved to local context: --name: myVNet, --subnet-name: mySubnet
{
"newVNet": {
"addressSpace": {
"addressPrefixes": [
"10.0.0.0/16"
]
},
...
}

az local-context show

Command group 'local-context' is experimental and not covered by customer support. Please use with discretion.
{
"all": {
"resource_group_name": "myGroup ",
"subnet_name": "mySubnet",
"vnet_name": "myVNet"
}
}

az local-context show --name vnet_name subnet_name

Command group 'local-context' is experimental and not covered by customer support. Please use with discretion.
{
"all": {
"subnet_name": "mySubnet",
"vnet_name": "myVNet"
}
}

az local-context delete --name resource_group_name

Command group 'local-context' is experimental and not covered by customer support. Please use with discretion.
Local context value is deleted. You can run az local-context show to show all available values.

az local-context show

Command group 'local-context' is experimental and not covered by customer support. Please use with discretion.
{
"all": {
"subnet_name": "mySubnet",
"vnet_name": "myVNet"
}
}

az local-context delete --all

Command group 'local-context' is experimental and not covered by customer support. Please use with discretion.
You are going to clear all local context value. Are you sure you want to continue this operation ? (y/n): y
Local context information in working directory D:\code\cli is cleared.

az local-context delete --all --purge

Command group 'local-context' is experimental and not covered by customer support. Please use with discretion.
You are going to delete local context persistence file. Are you sure you want to continue this operation ? (y/n): y
Local context persistence file in working directory D:\code\cli is deleted.

az local-context off

Command group 'local-context' is experimental and not covered by customer support. Please use with discretion.
Local context is turned off, you can run az local-context on to turn it on.

History Notes

[Component Name 1] BREAKING CHANGE: az command a: Make some customer-facing breaking change.
[Component Name 2] az command b: Add some customer-facing feature.

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