[Feature]: Register-ResourceProvider Wait for Registration to Complete

### Description of the new feature

The [az cli provider register](https://docs.microsoft.com/en-us/cli/azure/provider?view=azure-cli-latest) offers a --wait parameter when you register a resource provider, however the Azure PowerShell Register-Resource provider has no such option.

### Proposed implementation details (optional)

add a -wait switch to wait for the provider registration to be completed before continuing on.

Start at the Register-ResourceProvider cmdlet entry point and compare its behavior with the documented az cli provider register --wait option. Trace how registration currently returns, then verify that a new -Wait switch waits for provider registration to complete before the command continues.

Written by the indexing model from the issue text.