Add missing type hints to `synapse.app`. (#11287)

changelog.d/11287.misc

mypy.ini

synapse/app/__init__.py

synapse/app/_base.py

synapse/app/admin_cmd.py

synapse/app/generic_worker.py

synapse/app/homeserver.py

synapse/app/phone_stats_home.py

synapse/handlers/admin.py

synapse/logging/handlers.py

synapse/module_api/__init__.py

synapse/replication/tcp/resource.py

synapse/server.py

synapse/types.py

synapse/util/async_helpers.py

synapse/util/httpresourcetree.py

synapse/util/manhole.py