Need to prepare() the SQLiteMemoryDbPool before passing it to HomeServer constructor, as DataStore's constructor will want it ready

Start of converting PresenceHandler unit tests to use SQLiteMemoryDbPool - just the 'State' test case for now

Fix bug where we used an unbound local variable if we ended up rolling back the persist_event transaction

Killed an unexpected pagination trigger when the page load: paginateMore

Do this by synchronizing the m.room.member joined event from the events stream and the start of the pagination

Removed historical code: recents does not need to manage presences. It is already done by initialSync in eventStreamService