Fix Installed tab freeze from sync-over-async in GetPackageVersionsAsync

[jebriede]

Bug

Fixes: NuGet/Home#14964

Description

The PM UI's Installed tab froze for tens of seconds before showing any packages on slow feeds. The root cause is a sync-over-async call in NuGetPackageSearchService.GetPackageVersionsAsync: it read the still-running AllVersionsContextInfo background task via .Result before the method's first await, so the whole call ran synchronously and blocked the caller by roughly one registration round-trip per package. Because the package list view models are built on that thread, the list couldn't render until every package's version load completed.

This change awaits AllVersionsContextInfo once into a local and uses that for the null/count check and the return value, so the method is genuinely asynchronous and yields instead of blocking. The list now renders immediately while version/update info streams in. (It also removes a latent bug where the same ValueTask was consumed two or three times.)

PR Checklist

• Meaningful title, helpful description and a linked NuGet/Home issue
• Added tests
• Link to an issue or pull request to update docs if this PR changes settings, environment variables, new feature, etc.

[martinrrm]

I think we also need to add a loader indicator in the version's dropdown, if I understand correctly this will allow items in the scroll list show while we are fetching for the versions.

A quick fix could be making the dropdown disabled with "Loading package versions... " text while NuGetPackageSearchService.GetPackageVersionsAsync ends

[jebriede]

I think we also need to add a loader indicator in the version's dropdown, if I understand correctly this will allow items in the scroll list show while we are fetching for the versions.

A quick fix could be making the dropdown disabled with "Loading package versions... " text while NuGetPackageSearchService.GetPackageVersionsAsync ends

Some indicator that the versions are loading in the UX would be good. Please open an issue for this as a DCR so we can track that improvement.