Search backend: re-open #39501 against `main`
Created by: camdencheek
Turns out, github really doesn't like when you have two PRs open from the same branch. Auto-rebasing on main failed dramatically, but the first PR still merged, just into the branch it was based off of. This is the same PR as https://github.com/sourcegraph/sourcegraph/pull/39501, nothing has changed.
Test plan
Covered in original PR.