CSR Metadata request acts as a probe for ImdsV2

[Robbie-Microsoft]

This PR introduces ImdsV2 as a Managed Identity source, and focuses on executing a network request to get metadata to be used in the rest of the flow.

[neha-bhargava]

Need to undo the changes to public API to get the managed identity source

[neha-bhargava]

Why not keep this as static as well. The method to get the source was created static so that Azure Identity can detect if managed identity is available before creating the source. Was this discussed with them?

[Robbie-Microsoft]

@neha-bhargava, this method passes the Service Bundle through the ManagedIdentityClient's GetManagedIdentitySourceAsync method, and into ImdsV2ManagedIdentitySource, where the csr metadata probe uses things from the Service Bundle: IdType, UserAssignedId, RetryPolicyFactory, HttpManager, Logger, etc.

[Robbie-Microsoft]

@gladjohn Can you confirm that this would work with Azure Identity? Did you discuss with them?

[gladjohn]

thought, we agreed to keep this static @Robbie-Microsoft.

[Robbie-Microsoft]

The dev experience won't change for Azure SDK. They are still creating an instance of Managed Identity Application for their tests - they will be able to call this method from the managedAidentityApplication. You, @bgavrilMS and I can discuss over chat.