Room directory list API should record who made the room visible in the directory

This issue has been migrated from [#5059](https://github.com/matrix-org/synapse/issues/5059).

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`PUT /_matrix/client/r0/directory/list/room/{roomId}` - This doesn't record who did it
`PUT /_matrix/client/r0/directory/room/{roomAlias}` - This does, but it doesn't affect the visibility of the room in the directory

The visibility API (first endpoint) should record who did it. This isn't needed for the protocol to work, but it would be nice to have from a server admin perspective.

Start by locating the handlers for PUT /_matrix/client/r0/directory/list/room/{roomId} and PUT /_matrix/client/r0/directory/room/{roomAlias}, then compare how the latter records the actor. Done means the visibility endpoint records who changed the room's directory visibility without changing the protocol behavior.

Written by the indexing model from the issue text.