R1:5f939dcce0f8

Re-run config validation from `bin/search`

Summary:
Ref T12450. Normally, we validate config when:

- You restart the webserver.
- You edit it with `bin/config set ...`.
- You edit it with the web UI.

However, you can also change config by editing `local.json`, `some_env.conf.php`, a `SiteConfig` class, etc. In these cases, you may miss config warnings.

Explicitly re-run search config checks from `bin/search`, similar to the additional database checks we run from `bin/storage`, to try to produce a…