grid Add a feature switch to use @guardian/cql in the structured search component

What does this change?

Add a feature switch to toggle using @guardian/cql in the structured search component.

Todo:

[ ] ~Dates (I can see grid accepts e.g. date:"january 2014", but there's no chip — presumably we would like a chip?)~ I don't think dates are necessary to ship this, as the current chip implementation doesn't give a UI — so we can treat date-type inputs as TEXT for now, and improve down the line
[x] Handle non-wordchar chip keys
[x] Types for any types in migrated service
[x] alt-click on fields should correctly add negations — at the moment, they are included in the chip key
[x] negations should survive a round-trip through the URL
[x] field aliases should not show options where none exist
[x] Layout issues for typeahead when navigating with arrow keys
[ ] Placeholder
[ ] Keyboard shortcuts (e.g. l) trigger when typing in input
[ ] 'Clear query' button doesn't work
[ ] Little ghost suggestion when clicking into chip keys/values — we should show suggestions
[ ] Sentry sees [TypeaheadPopover]: No action handler has been registered by the popover renderer
[ ] I guess I got rid of the scrollbars in the suggestions somehow? 😅
[ ] Add descriptions for fields, or get rid of them entirely?
[x] Styling