[2.10] Fleet Improvements

[richard-cox]

Summary

Fixes #12232

Occurred changes and/or fixed issues

• Performance Fix
  • go back to using git repo status cluster ready / desired stats instead of costly clusterResourceStatus (churn can call this a LOT)
  • Improve load time of fleet cluster detail page
• Bug Fix
  • Using targetClustersReady and targetClusters doesn't seem to work in some cases, revert back to previous
• General Fixes
  • Fix weird fleet cluster list column alignment

Areas or cases that should be tested

As per issue

Areas which could experience regressions

• Git repo detail page loads fine (on navigation and refresh)
• Fleet Dashboard page shows correct stats for
  • clusters ready - now matches repo list's cluster stats
  • bundles ready - no change (except 0 now displays as such, rather than ?)
  • resources ready - no change (except 0 now displays as such, rather than ?)

Checklist

• The PR is linked to an issue and the linked issue has a Milestone, or no issue is needed
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• The PR has automated tests or clear instructions for manual tests and the linked issue has appropriate QA labels, or tests are not needed
• The PR has reviewed with UX and tested in light and dark mode, or there are no UX changes