Add tests for read and write hooks

Most of the work so far lives on this branch. I've committed to taking a data-first approach for now as it feels more straightforward, despite react testing library's preference for DOM-oriented testing. Been running into some annoying issues around React Query updates sometimes not being applied and available within a test, but otherwise things seem to work as expected.

There's going to be a good amount of overlap with how the e2e tests in core work. The one difference that I want to make sure is tested here is the end-user hook APIs we land on and making sure the behaviors of these hooks (e.g. invalidation, state updates, etc) are expected