Brings back EventPersister in discovery of background services

[chrisguidry]

In the prior work on this (#16913) we needed to
maintain an explicit set of modules from which to discover services, and
I missed the modules that include the EventPersister and the
EventLogger (a debugging-only service). This meant that under most
circumstances, because the event_persister module wasn't imported, we
wouldn't run it in either API or background processes.

Here I'm adding a test that confirms the exact subsets of services we
should run, just to avoid any quiet failures like this.

Checklist

• This pull request references any related issue by including "closes <link to issue>"
  • If no issue exists and your change is not a small fix, please create an issue first.
• If this pull request adds new functionality, it includes unit tests that cover the changes
• If this pull request removes docs files, it includes redirect settings in mint.json.
• If this pull request adds functions or classes, it includes helpful docstrings.

[codspeed-hq]

CodSpeed Performance Report

Merging #17240 will not alter performance

_{Comparing include-event-persister (f885834) with main (a7e94ad)}

Summary

✅ 2 untouched benchmarks