Implement authority validation for isolated cloud. [Internal workitem here](https://identitydivision.visualstudio.com/Engineering/_workitems/edit/1055278) and [internal design doc here](https://identitydivision.visualstudio.com/DevEx/_git/AuthLibrariesApiReview/pullrequest/1479?_a=files&path=/AuthorityValidation/airgap_authority_validation.md).
