CLN: Remove unused fixtures
LGTM Does pytest expose a way to figure out what is / isn't being used? > Does pytest expose a way to figure out what is / isn't being used?

There's a plugin (which is what I was using here) but not sure how well-maintained it is: https://github.com/jllorencetti/pytest-deadfixtures thanks!

also as a possible issue / followup. we ideally want to surface the same / similar fixtures to the top level (and similarly push down ones that are ownly used beneath a particular sub-tree to a lower level). not sure if there is an easy way to do this.