Panel search: abort previous requests

[distantnative]

This PR …

Fixes

• Panel search: previous search requests are aborted when new ones are sent to the backend
  Search in panel shows old results when response times from server vary #6409

For review team

• Add changes & docs to release notes draft in Notion

[bastianallgeier]

There are now quite a few situations where the search is showing "No results" while there's still a search going on in the background that will eventually deliver results. It feels a bit confusing.

[distantnative]

@bastianallgeier tricky one. I think we cannot work with the current boolean isLoading then but rather need a counter incrementing when a request starts, decrementing when one is finished/aborted. What do you think?

[bastianallgeier]

Yep, makes sense. I also saw yesterday that we need to improve the "no results" part. It should only be shown if nothing is loading and maybe show a "Searching …" placeholder instead if there are no results in the list but loading is still happening.

[distantnative]

@bastianallgeier I tried to change it, but I am missing something, it still happens for me. Mostly when deleting parts of the query with backspace.