search pages: improve various queries

Created by: rvantonder

I checked most manually, see inline comments for each. Overall I think there's little value in showing a query that doesn't have any results, so we should just remove those, or replace them with a representative example that does have results.

I'm aware of the ones that don't show results because repos are not indexed (the android one), but I don't think this applies to the react-hooks ones.