[WIP] persist: upsert cas / read latest state as single query

[pH14]

Still WIP... saw that we're getting cas mismatches on ~40-50% of our compare_and_set calls steady-state. This rewrites the query so we can both insert || read the latest state before retrying, in case of cas mismatch.

This is unmergeable until https://github.com/MaterializeInc/materialize/pull/13954 and a good round of Maelstrom testing

Motivation

Tips for reviewer

Checklist

• [ ] This PR has adequate test coverage / QA involvement has been duly considered.

• [ ] This PR evolves an existing $T ⇔ Proto$T mapping (possibly in a backwards-incompatible way) and therefore is tagged with a T-protobuf label.

• [ ] This PR includes the following user-facing behavior changes:

[maddyblue]

Cockroach change merged!

[pH14]

Amazing! Thank you Matt 🙇

[maddyblue]

A rebase will fix the test failure.

[pH14]

Downgraded the interesting-ness of this PR a bit. I couldn't find a way to fast-path-insert-or-read in a single RTT to CRDB, and I removed the pipeline read for now -- we can reexamine what our contention looks like post-https://github.com/MaterializeInc/materialize/pull/14217