[Feature Request] Add support for Managed Identity

[bgavrilMS]

Support in MSAL .NET - https://learn.microsoft.com/en-us/entra/msal/dotnet/advanced/managed-identity

More in-depth technical spec here. DotNet implementation here. All MSALs support it (Java, Py, NodeJS).

• [ ] Get the PR / CI builds working again (most likely need to move them from GitHub to ADO)
• [ ] Public API support (new client, ways to specify between UAMI and SAMI, disable token cache serialization extensibilty)
• [ ] Detect MSI source + public API for Azure SDK for this (probing API ... see .NET too)
• [ ] Code up the 5 MSI sources (check Azure SDK's implementation, should be mostly copy-paste)
  • [ ] Error handling code
  • [ ] https://github.com/AzureAD/microsoft-authentication-library-for-dotnet/issues/4837
• [ ] Manual testing of each MSI source (this is the most consuming task). Do negative testing as well to check error handling.
• [ ] Static caching of all MSI tokens (including adding a property TokenSource on the AutheticationResult)
• [ ] Retry policy for MSI (create public API to disable retry policies, abstract retry policy in MSAL, add linear retry 3 times with 1s interval to MSI)
• [ ] Update Sample with MSAL Go implementation - https://learn.microsoft.com/en-us/entra/msal/dotnet/advanced/managed-identity
• [ ] Update docs
• [ ] Review support for FIC, update samples etc.