[Feature]: Add App Configuration Data Plane commands

[jeffreyrivor]

Description of the new feature

The Az.AppConfiguration module has commands for the control plane leveraging the generated AutoRest APIs, but does not have the data plane (the "Feature manager" and "Configuration explorer" operations in Azure portal). Seems like it should be possible to expose the data plane REST APIs in the PowerShell module; these are already available in the Azure CLI.

Proposed implementation details (optional)

Both the underlying azure-api-rest-specs and the generated AutoRest APIs (for example, the ConfigurationStoresListKeyValue* methods in AppConfiguration.cs) have the needed data plane specifications. It seems like it may be as simple as adding the AutoRest configuration to expose the generated methods as a cmdlet.

[dingmeng-xue]

Thanks @jeffreyrivor . It is on our feature list but it not planned yet because of lack of resource. We will visit this module soon.

[mjrousos]

It would be great to be able to manage App Configuration feature flags from the Az.AppConfiguration module. That is possible from AZ CLI (az appconfig feature), but unfortunately not from Az.AppConfiguration as far as I can tell.