Expand synapse.module_api.__all__ to include more of the publicly exposed types/helpers (#20107)

I *think* the intention is that `__all__` can be used to access all the
types that are exposed via the module API. However, some of them are
missing.

This PR adds those that are directly referenced but were not exposed.
There are some others that are indirectly referenced that I've not
included (e.g. `synapse.spam_checker_api.RegistrationBehaviour`).

changelog.d/20107.misc

@@ -0,0 +1 @@
+Declare types that already appear in the module API's public signatures (such as `Requester`, `SynapseRequest` and `UserInfo`) in `synapse.module_api.__all__`.

synapse/module_api/__init__.py

@@ -194,14 +194,21 @@ __all__ = [
     "run_in_background",
     "run_as_background_process",
     "cached",
+    "CachedFunction",
     "NOT_SPAM",
     "UserID",
+    "DomainSpecificString",
     "DatabasePool",
     "LoggingTransaction",
     "DirectServeHtmlResource",
     "DirectServeJsonResource",
+    "SimpleHttpClient",
+    "SynapseRequest",
     "ModuleApi",
+    "AccountDataManager",
+    "PublicRoomListManager",
     "PRESENCE_ALL_USERS",
+    "UserPresenceState",
     "LoginResponse",
     "JsonDict",
     "JsonMapping",
@@ -209,7 +216,13 @@ __all__ = [
     "StateMap",
     "ProfileInfo",
     "RoomAlias",
+    "RoomID",
+    "Requester",
+    "UserInfo",
+    "UserIpAndAgent",
     "UserProfile",
+    "Absent",
+    "AbsentType",
     "RatelimitOverride",
     "MediaUploadLimit",
 ]