Tag filtering only show tags from visible PRs, and very slow when increasing PR visibility count

[helmesjo]

Describe the bug
When trying to filter on PR tags it only shows a list of tags corresponding to the currently visible subset of PRs. Increasing the number of visible/loaded PRs "works", but fetching the tags is extremely slow (1+ minute each time the page is refreshed).

To Reproduce
Steps to reproduce the behavior:

1. Go to Pull Request Manager Hub
2. Go to Preferences and limit Top Completed/Abandoned PRs to say 1.
3. Notice that the tag filter only showing tags used by this PR.
4. Redo 2. but set it to say 1000.
5. Notice the tag filter dropdown loading for a long time.
   Expected behavior
   I'm pretty sure the REST API (at least) supports to fetching all tags, at least with the tag list on PBIs it shows all and that is visibly instant.

Screenshots

Desktop:

• OS: Windows 11
• Browser: Edge
• Version: v2.0