Properly typecheck types.http (#14988)

* Tweak http types in Synapse

AFACIS these are correct, and they make mypy happier on tests.http.

* Type hints for test_proxyagent

* type hints for test_srv_resolver

* test_matrix_federation_agent

* tests.http.server._base

* tests.http.__init__

* tests.http.test_additional_resource

* tests.http.test_client

* tests.http.test_endpoint

* tests.http.test_matrixfederationclient

* tests.http.test_servlet

* tests.http.test_simple_client

* tests.http.test_site

* One fixup in tests.server

* Untyped defs

* Changelog

* Fixup syntax for Python 3.7

* Fix olddeps syntax

* Use a twisted IPv4 addr for dummy_address

* Fix typo, thanks Sean

Co-authored-by: Sean Quah <8349537+squahtx@users.noreply.github.com>

* Remove redundant `Optional`

---------

Co-authored-by: Sean Quah <8349537+squahtx@users.noreply.github.com>

tests/http/test_additional_resource.py

@@ -11,28 +11,34 @@
 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 # See the License for the specific language governing permissions and
 # limitations under the License.
+from typing import Any
 
+from twisted.web.server import Request
 
 from synapse.http.additional_resource import AdditionalResource
 from synapse.http.server import respond_with_json
+from synapse.http.site import SynapseRequest
+from synapse.types import JsonDict
 
 from tests.server import FakeSite, make_request
 from tests.unittest import HomeserverTestCase
 
 
 class _AsyncTestCustomEndpoint:
-    def __init__(self, config, module_api):
+    def __init__(self, config: JsonDict, module_api: Any) -> None:
         pass
 
-    async def handle_request(self, request):
+    async def handle_request(self, request: Request) -> None:
+        assert isinstance(request, SynapseRequest)
         respond_with_json(request, 200, {"some_key": "some_value_async"})
 
 
 class _SyncTestCustomEndpoint:
-    def __init__(self, config, module_api):
+    def __init__(self, config: JsonDict, module_api: Any) -> None:
         pass
 
-    async def handle_request(self, request):
+    async def handle_request(self, request: Request) -> None:
+        assert isinstance(request, SynapseRequest)
         respond_with_json(request, 200, {"some_key": "some_value_sync"})
 
 
@@ -41,7 +47,7 @@ class AdditionalResourceTests(HomeserverTestCase):
     and async handlers.
     """
 
-    def test_async(self):
+    def test_async(self) -> None:
         handler = _AsyncTestCustomEndpoint({}, None).handle_request
         resource = AdditionalResource(self.hs, handler)
 
@@ -52,7 +58,7 @@ class AdditionalResourceTests(HomeserverTestCase):
         self.assertEqual(channel.code, 200)
         self.assertEqual(channel.json_body, {"some_key": "some_value_async"})
 
-    def test_sync(self):
+    def test_sync(self) -> None:
         handler = _SyncTestCustomEndpoint({}, None).handle_request
         resource = AdditionalResource(self.hs, handler)