Add missing type hints to `synapse.logging.context` (#11556)

changelog.d/11556.misc

mypy.ini

stubs/txredisapi.pyi

synapse/federation/federation_server.py

synapse/handlers/federation.py

synapse/handlers/initial_sync.py

synapse/handlers/message.py

synapse/http/federation/matrix_federation_agent.py

synapse/logging/context.py

synapse/util/async_helpers.py

synapse/util/caches/cached_call.py

synapse/util/file_consumer.py

tests/util/test_logcontext.py