delete the pools package

[p0mvn]

          This is a good cleanup step.

Without spending tons of time digging into the code, I think the next step to evetually delete the pools package (or help us be ready to) would be to copy over any imports directly from the pools package into /packages/server/src/queries/sidecar/router.ts (like error types, the router interface, etc).

Basically removing references into the pools package. Then when the tRPC migration is complete and all legacy pools queries are deleted, we can just delete that package in entirety.

Originally posted by @jonator in #3757 (review)