Swap codeinsights-db docker image to be based off postgres instead of Timescale
Created by: caugustus-sourcegraph
Switches the base for codeinsights-db to Postgres, away from Timescale. This swap preserves the existing postgres uid used by the container, to avoid requiring users to migrate file permissions.
This PR restores the changes from https://github.com/sourcegraph/sourcegraph/pull/32616, with fixes for the tests that were failing before.
Test plan
Tests should pass