Add acquiring ACR access token using Azure.Identity and allow unauthenticated ACR endpoints

[adityapatwardhan]

PR Summary

• Acquire ACR access token using Azure.Identity
• To acquire ACR access token we go through the following steps
  • Check if a credential is provided when registering the repository, if it then use it.
  • If no credential provided at registration then
    • Check if the ACR endpoint can be accessed without a token
    • If not, try using Azure.Identity to get the az access token, then ACR refresh token and then ACR access token.

PR Context

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[alerickson]

resolves #1580

[anamnavi]

LGTM