Add common changes to support Azure Batch AAD

[matthchr]

Description

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[matthchr]

This PR is in preparation for adding Batch AAD support. See #4762 for the official support.

[matthchr]

@markcowl please take a look when you get a chance

[markcowl]

Requested test changes for regression protection and type conversion for display types. Otherise, LGTM

[markcowl]

can we add in tests that verify this value - we have tests that check the output type, and tests that check the value that is saved in the context

[matthchr]

Okay, I have updated the TypeConversionTests as well (I hadn't realized they were there earlier).

Can you point me to the test classes/methods for any other tests which I should update?

[markcowl]

I think we want to use BatchAudience as well

[matthchr]

As an alias you mean? Will add it.

[matthchr]

This is done

[markcowl]

Note, I think you will also need to change the constructors and type conversion operators for PSAzureEnvinronment to include this value. If you add this value into existing test validation overt these types, you'll see the code you need to change.

[matthchr]

This was already done I think, right? I made the change to PSAzureEnvironment(PSObject other) already, and to Equals in PSAzureEnvironment - Did I need to do something else too?

[markcowl]

on demand run here: https://azuresdkci.westus2.cloudapp.azure.com/view/PowerShell/job/powershell-demand/79/

[matthchr]

@markcowl It looks like the on-demand run failed? I am not sure if it's related to this change or not though (logs are hard to parse...)