POC: Fully separate query_service from weave. Most weave tests passing

[shawnlewis]

This has the query_service completely separated from weave. Most of the weave unit tests pass. I think the remaining failures are test setup issues, not functional.

So if you checkout this PR you can do: cd weave; pytest and see the tests pass

What I did:

• move weave/legacy to query_service
• try to run pytest in the weave dir
• fix all the issues

Remaining steps:

• make init.py for query_service and ensure you can import it
• get query_service unit tests passing. I did not do this here. I copied conftest.py into query_service, and wandb_system_tests_conftest.py, but I didn't fix setup paths and import issues that would arise.
• fix CI to run both suites of tests independently (and only when one or the other changes)
• cleanup pass in weave: cull unused symbols. This should remove a lot of junk in conftest and other places
• i moved a modified copy of context_state.py into weave/trace/client_context. Most of the stuff in there can be removed, and that's probably not the right directory for it
• fix core stuff that relies on query_service to build it properly