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/push/push_tools.py

@@ -13,7 +13,6 @@
 # limitations under the License.
 from typing import Dict
 
-from synapse.api.constants import ReceiptTypes
 from synapse.events import EventBase
 from synapse.push.presentable_names import calculate_room_name, name_from_member_event
 from synapse.storage.controllers import StorageControllers
@@ -24,30 +23,24 @@ async def get_badge_count(store: DataStore, user_id: str, group_by_room: bool) -
     invites = await store.get_invited_rooms_for_local_user(user_id)
     joins = await store.get_rooms_for_user(user_id)
 
-    my_receipts_by_room = await store.get_receipts_for_user(
-        user_id, (ReceiptTypes.READ, ReceiptTypes.READ_PRIVATE)
-    )
-
     badge = len(invites)
 
     for room_id in joins:
-        if room_id in my_receipts_by_room:
-            last_unread_event_id = my_receipts_by_room[room_id]
-
-            notifs = await (
-                store.get_unread_event_push_actions_by_room_for_user(
-                    room_id, user_id, last_unread_event_id
-                )
+        notifs = await (
+            store.get_unread_event_push_actions_by_room_for_user(
+                room_id,
+                user_id,
             )
-            if notifs.notify_count == 0:
-                continue
+        )
+        if notifs.notify_count == 0:
+            continue
 
-            if group_by_room:
-                # return one badge count per conversation
-                badge += 1
-            else:
-                # increment the badge count by the number of unread messages in the room
-                badge += notifs.notify_count
+        if group_by_room:
+            # return one badge count per conversation
+            badge += 1
+        else:
+            # increment the badge count by the number of unread messages in the room
+            badge += notifs.notify_count
     return badge