Instant Search: Improve Filtering UX

Currently filtering helps the user navigate down into a rabbit hole, but does not help the user get out, or hop between rabbit holes (maybe gopher or prairie dog holes are a better analogy).

Partly the existing filtering always ANDs the filters together, but that causes the filters to disappear as the user applies more. This does mean that the user does not hit a dead-end, but it also does not give the user more options.

Some ideas:
- [x] Add a "Clear filters" link in the filter list (this is what the existing JP Search does
- [ ] Add suggested alternative filters at the bottom of the results or on the sidebar
- [ ] Add suggested filters to remove. Maybe based on the order in which the user added filters.

No files, tests, or entry points are named, so start by locating the Instant Search filtering UI and reviewing the existing Clear filters behavior. Define and implement an agreed approach for alternative filters or filter-removal suggestions, with the filtering flow making those options visible and usable.

Written by the indexing model from the issue text.