Speed up get_unread_event_push_actions_by_room (#13005)

Fixes #11887 hopefully.

The core change here is that `event_push_summary` now holds a summary of counts up until a much more recent point, meaning that the range of rows we need to count in `event_push_actions` is much smaller.

This needs two major changes:
1. When we get a receipt we need to recalculate `event_push_summary` rather than just delete it
2. The logic for deleting `event_push_actions` is now divorced from calculating `event_push_summary`.

In future it would be good to calculate `event_push_summary` while we persist a new event (it should just be a case of adding one to the relevant rows in `event_push_summary`), as that will further simplify the get counts logic and remove the need for us to periodically update `event_push_summary` in a background job.

synapse/storage/databases/main/push_rule.py

@@ -110,9 +110,9 @@ def _load_rules(
 # the abstract methods being implemented.
 class PushRulesWorkerStore(
     ApplicationServiceWorkerStore,
-    ReceiptsWorkerStore,
     PusherWorkerStore,
     RoomMemberWorkerStore,
+    ReceiptsWorkerStore,
     EventsWorkerStore,
     SQLBaseStore,
     metaclass=abc.ABCMeta,