rephrase the OPTIONS and unrecognised request handling so that they look
similar to the common flow.

We add a new storage function to get a paritcular type of room account
data. This allows us to prefill the cache when updating that acount
data.

Make repl send_event idempotent and retry on timeouts

If we treated timeouts as failures on the worker we would attempt to
clean up e.g. push actions while the master might still process the
event.

Calculate push actions on worker

Move storage functions for push calculations

This will allow push actions for an event to be calculated on workers.

Fix missing invalidations for receipt storage

Split out RoomMemberStore

Split AS stores

Batch inserts into event_push_actions_staging

Ensure all push actions are deleted from staging

Split out EventPushActionWorkerStore

Split out get_events and co into a worker store

Split PusherStore

Split PushRulesStore

Split AccountDataStore and TagStore