[Feature]: Add App Configuration Data Plane commands

### 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](https://docs.microsoft.com/en-us/cli/azure/appconfig/kv?view=azure-cli-latest#az-appconfig-kv-list).

### Proposed implementation details (optional)

Both the underlying [azure-api-rest-specs](https://github.com/Azure/azure-rest-api-specs/tree/main/specification/appconfiguration/data-plane) and the generated AutoRest APIs (for example, the `ConfigurationStoresListKeyValue*` methods in [AppConfiguration.cs](https://github.com/Azure/azure-powershell/blob/main/src/AppConfiguration/generated/api/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.