Please restore the ability to see membership changes in public rooms

Ideally make it configurable because many probably don't want to see it. Some do (hi 👋🏼) in some cases and hiding it entirely removes the ability to see some information about what is going on in the room.

Start by locating the code that filters or displays membership changes in public-room timelines, then check how existing room-level display settings are represented. Define the configurable behavior so membership changes can be shown again without forcing them on everyone, and verify both setting choices in the Android UI.

Written by the indexing model from the issue text.