ACR Tokens support for authentication

The feature is still in preview, but you can generate tokens for ACR that are (optionally) scoped to specific repositories and with limited permissions.

Having the ability to use these tokens for authentication would be a huge improvement.

Docs:
https://docs.microsoft.com/en-us/azure/container-registry/container-registry-repository-scoped-permissions

No files, tests, or entry points are named. Start by reading the linked Azure documentation on repository-scoped ACR tokens, then trace the existing image-registry authentication flow; done means ACR tokens can authenticate with optional repository scope and limited permissions.

Written by the indexing model from the issue text.