Fix Azure DevOps nuget v2 feed download

[o-l-a-v]

PR Summary

When downloading from Azure DevOps Artifacts feeds with NuGet v2, the package ID must be lowercase.

I read that here:

• https://blogs.blackmarble.co.uk/rfennell/downloading-nuget-packages-with-system.net.webclient/

PR Context

Partially fixes #1491

PR Checklist

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• [x] Make sure all .h, .cpp, .cs, .ps1 and .psm1 files have the correct copyright header
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  • [ ] [Documentation needed]()
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[o-l-a-v]

Can't add test as there is no public test instance for this AFAIK. Ref feature request:

• 1714

[alerickson]

We previously had ADO tests specifically for their v3 endpoint, I just added a file to include the same testing for the v2 endpoint as well.