Implement Credential-Based Managed Identity Authentication

[gladjohn]

Fixes #4411

Changes proposed in this request

• This new implementation focuses on supporting Managed Identity authentication using credentials. It caters specifically to scenarios where Managed Identity is utilized using a machine key as a source
• MSAL creates an in-memory certificate using the MI key, uses the certificate to get the credential, passes the credential as an assertion to ESTS-R over MTLS with the same certificate
• HttpManager changes have been made to support MTLS
• Added NET472, as this is the minimum supported for MI with credential as a source
• Adds claims and capabilities support for Managed Identity
• Supports SLC on Windows VMs where a software or a machine key has been provisioned

Please review SLC board for a full list of work items.

Testing

• unit tests
• need to add integration tests

Performance impact none

Documentation n/a

[SimonCropp]

re "Documentation: n/a". this adds new public apis. how can there be no associated documentation?

[pmaytak]

@gladjohn Should this be set to draft; you're splitting it into a separate PR?