Lots of different module apis is not easy to maintain.
Rather than adding yet another ModuleApi(hs, hs.get_auth_handler()) incantation, first add an hs.get_module_api() method and use it where possible.
This PR allows `ThirdPartyEventRules` modules to view, manipulate and block changes to the state of whether a room is published in the public rooms directory.
While the idea of whether a room is in the public rooms list is not kept within an event in the room, `ThirdPartyEventRules` generally deal with controlling which modifications can happen to a room. Public rooms fits within that idea, even if its toggle state isn't controlled through a state event.
Fixes https://github.com/matrix-org/synapse/issues/7683
Broke in: #7649
We had a `yield` acting on a coroutine. To be fair this one is a bit difficult to notice as there's a function in the middle that just passes the coroutine along.