Return immutable objects for cachedList decorators (#16350)

changelog.d/16350.misc

synapse/appservice/__init__.py

synapse/appservice/api.py

synapse/appservice/scheduler.py

synapse/handlers/appservice.py

synapse/handlers/e2e_keys.py

synapse/handlers/initial_sync.py

synapse/handlers/receipts.py

synapse/handlers/sync.py

synapse/handlers/typing.py

synapse/push/bulk_push_rule_evaluator.py

synapse/storage/databases/main/appservice.py

synapse/storage/databases/main/devices.py

synapse/storage/databases/main/end_to_end_keys.py

synapse/storage/databases/main/events_worker.py

synapse/storage/databases/main/keys.py

synapse/storage/databases/main/presence.py

synapse/storage/databases/main/push_rule.py

synapse/storage/databases/main/receipts.py

synapse/storage/databases/main/relations.py