V2/Server: Prevent NRE when NormalizedVersion is missing

[sean-r-williams]

PR Summary

This PR conditionalizes adding NormalizedVersion to the additionalMetadata property on V2 server responses. This should resolve #1486.

PR Context

Services like Artifactory do not present a NormalizedVersion property in their metadata when querying via the NuGet v2 API. This causes PSResourceInfo.TryConvertFromXml() to NRE.

The change in this PR skips trying to add this property to AdditionalMetadata if the server did not present a NormalizedVersion property.

This naturally means AdditionalMetadata is not guaranteed to include this field on responses from v2 Server feeds, but I don't see any documentation indicating this is guaranteed.

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[sean-r-williams]

I tried running tests locally - it seems the docs are a bit out of date (see #1486 (comment)) so I made a best-effort approach (h/t to jborean on the PowerShell Discord for the suggestion of using test.yml)

Running Invoke-ModuleTests -Type Functional seems to work, with the exception of GitHub Packages. These tests appear to depend on PATs from AzDO, so I'm not sure if there's a good way to run them locally.

[alerickson]

@sean-r-williams unfortunately easily testing against GitHub packages can only really be done with CI. But your PR looks good so I'll merge in. Thanks for opening the related issue and a double thanks for the PR to fix it!

[sean-r-williams]

Thanks @alerickson! Is there any ETA from your team on when 1.0.2 is expected to be released?

This is blocking some of our internal development workflows (we can't use PSResourceGet 1.0.1 because of this bug, and PowerShellGet only works for module packages in Artifactory - not script packages). I want to make sure we adjust our delivery timelines accordingly so we don't churn before 1.0.2 is available.