Faster room joins: fix race in recalculation of current room state (#13151)

Bounce recalculation of current state to the correct event persister and
move recalculation of current state into the event persistence queue, to
avoid concurrent updates to a room's current state.

Also give recalculation of a room's current state a real stream
ordering.

Signed-off-by: Sean Quah <seanq@matrix.org>