Access app role assignments for service principals

**Is your feature request related to a problem? Please describe.**
When interacting with Azure Active Directory, creating app registrations, creating service principals and granting consent for both role- and delegated permissions, there is an unpredictable delay between when the API accepts a resource changing request and when the change is actually visible by querying the API.
Because of this we have to continuously query the API and wait for changes to become effective and it seems we can do so for everything but app role assignments.

**Describe the solution you'd like**
Make it possible to query for app-role-assignments under service principals, as it is possible to do using the Graph on _https://graph.microsoft.com/beta/servicePrincipals/{id}/appRoleAssignedTo_

**Describe alternatives you've considered**
I will have to manually query Graph instead of using the CLI

**Additional context**
Link to the Graph docs: https://docs.microsoft.com/en-us/graph/api/approleassignment-get