search: add new lucky query generator

Created by: rvantonder

See the updated docstring.

Very excited now because this generates exactly the strategy I want to just add "whatever" rules without thinking about composition and just have the generator do the hard work.

I won't lie: the generation code is pretty sophisticated and there's quite a bit of state accounting, so I've tried to separate it into phases (with minor code duplication) rather "less duplication but more spagehtti".

Test plan

Still unused, will activate it in a next PR.