rework search api to allow searching on multiple caches at once

[icewind1991]

Changes file search from having each storage's cache perform the cache to asking each cache for how to filter search results, combining all filters from every cache and running the search in a single query.
The results are then passed to the caches again to allow post-processing before finally turning them into the final result objects.

This way there is only a single query required for the search no matter how many storages a user has access to, this does come at the cost of a more complex query but it should still be a good improvement overall

[blizzz]

Just skimmed, did not see anything that is very obvious off.

Please check the code scanning findings, they seem reasonable.

[icewind1991]

rebase fixed ci :)

[putt1ck]

Can this be backported to 21?