Merge remote-tracking branch 'origin/release-v1.20.0' into develop

changelog.d/8264.misc

changelog.d/8266.misc

changelog.d/8270.feature

changelog.d/8271.bugfix

changelog.d/8274.feature

synapse/push/bulk_push_rule_evaluator.py

synapse/storage/databases/__init__.py

synapse/storage/databases/main/__init__.py

synapse/storage/databases/main/event_push_actions.py

synapse/storage/prepare_database.py

synapse/storage/util/id_generators.py