Merge pull request #8548 from matrix-org/rav/deferred_cache

changelog.d/8548.misc

synapse/replication/slave/storage/client_ips.py

synapse/storage/databases/main/client_ips.py

synapse/storage/databases/main/devices.py

synapse/storage/databases/main/events_worker.py

synapse/util/caches/deferred_cache.py

synapse/util/caches/descriptors.py

synapse/util/caches/lrucache.py

tests/storage/test__base.py

tests/test_metrics.py

tests/util/caches/test_deferred_cache.py

tests/util/caches/test_descriptors.py