[Eng]: Return a more explicit error message when New-AzADServicePrincipal hit MS Graph latency

[dcaro]

Description

Creating a service principal with a role may fail due to latency before the principal can be queried in Graph
After executing New-AzADServicePrincipal -DisplayName "serviceprincipalname" -Role Contributor
you may receive the following error:

New-AzRoleAssignment: /home/azureuser/.local/share/powershell/Modules/Az.Resources/5.2.0/MSGraph.Autorest/custom/New-AzADServicePrincipal.ps1:766
Line |
 766 |            $ra = New-AzRoleAssignment @param
     |                  ~~~~~~~~~~~~~~~~~~~~~~~~~~~
     | Operation returned an invalid status code 'BadRequest'

In the debug traces, we see the following error returned:

Body:
{
  "error": {
    "code": "PrincipalNotFound",
    "message": "Principal xxxxxxxxx does not exist in the directory xxxxxxxxxx."
  }
}

[dcaro]

@VeryEarly seems that we should follow this https://docs.microsoft.com/en-us/azure/role-based-access-control/role-assignments-rest#new-service-principal

[dcaro]

@jiasli FYI, let's have a consistent approach on this.