Restore support for dogfood/private cloud subscription local testing

This does not appear to be fully supported in the latest versions of Az.Resources (5.2.0) due to the change to use the MSGraph API instead of the AAD graph API. The `Get-AzAdServicePrincipal` and `Get-AzAdUser` calls no longer work with the way we are using them. Currently, local testing can work around this by manually provisioning a service principal and passing in the `Provisioner` parameter set including `ProvisionerApplicationOid` to the `New-TestResources.ps1` script.

Related fix for CI: https://github.com/Azure/azure-sdk-tools/pull/2592

[Internal discussion reference link](https://teams.microsoft.com/l/message/19:59dbfadafb5e41c4890e2cd3d74cc7ba@thread.skype/1642620368991?tenantId=72f988bf-86f1-41af-91ab-2d7cd011db47&groupId=3e17dcb0-4257-4a30-b843-77f47f1d4121&parentMessageId=1642620368991&teamName=Azure%20SDK&channelName=Engineering%20System%20%F0%9F%9B%A0%EF%B8%8F&createdTime=1642620368991)