persist/materialized: default to using postgres for consensus

[ruchirK]

This commit also changes testdrive to use Postgres during CI.

Motivation

Tips for reviewer

Testing

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

Release notes

This PR includes the following user-facing behavior changes:

[benesch]

👍🏽 on the idea, but I don't think it's going to be nearly this simple! The default PostgreSQL URL needs to be something that works on your local machine if you've got PostgreSQL running locally and configured with trust authentication (postgres://$USER, basically). We can resurrect the old logic from sqllogictest that handled this, because rust-postgres doesn't quite cut it out of the box. Then we'll need to install postgres in the materialized Docker image (not the materialized-slim Docker image), and override the --persist-consensus-url in the Docker image's CMD.

Does that make sense? I've got to run for the next hour, can explain more later!

[ruchirK]

I think the first part makes sense, but the second part is a bit unclear to me because I don't understand why we need postgres in the mz docker container itself. Per our conversation in the meeting I'll wait for you to pick off these three pieces, and I'll prep the pr that gets rid of the sqlite consensus impl after that

[benesch]

I think the first part makes sense, but the second part is a bit unclear to me because I don't understand why we need postgres in the mz docker container itself.

The materialize/materialized container needs to continue to work as a standalone container. Can't rely on it being run in mzcompose where every composition turns on a sidecar PostgreSQL container!