Improve support for assigning a user-assigned identity & roles to a function app

[MicroFish91]

Closes #4565

Summary:

• Allow users to assign newly created UAID to function apps
• Add location provider filtering for UAID in DTS flow
• Misc. improvements to the step responsible for assigning identities to a function app
• Update the roles callback to allow async; update DTS role assignment so that it leverages this to check for role necessity at the time of step execution
• Fix an issue where resources with the same name under the identity view were not being shown properly