Support Azure Arc managed identity

[cataggar]

Here it is in C#:
https://github.com/Azure/azure-sdk-for-net/blob/main/sdk/identity/Azure.Identity/src/AzureArcManagedIdentitySource.cs

Please let us know if this is something you need.

Like AppServiceManagedIdentityCredential and VirtualMachineManagedIdentityCredential, this would use the ImdsManagedIdentityCredential.

[heaths]

This should not be exposed publicly, but only through #1536.