bookmarks loading spinner might keep on spinning if there are no saved bookmarks
while its not visible on the screen (unless you open the bookmarks dropdown) it should stop displaying the spinner once the API response was completed.
fixes #22055 - update bookmark loading status.
This PR both fixes the issue reported by not showing spinner if
there is an empty set of saved bookmarks (it shows None found)
It also adds missing tests cases for spinner, error and empty
result sets, and replaces the loader component from patternfly-react