- Distinguish between tests of the incremental updates (handler) versus
  the initial background process (storage)
- Add test cases to futher probe that initial background process
- Add test case to check that reactivated users are added back to the directory

I don't fully understand why this was needed, but without this I was
missing entries from the users table that upcoming changes are about to
expect. (Was getting failures to select from the users table because
there were missing rows.)

can't see how to correctly configure the homeserver, so let's hack it

Handled in separate PR #10762

Co-authored-by: reivilibre <38398653+reivilibre@users.noreply.github.com>