Consider deprecating the `event` emit event due to confusion

Nobody has claimed this yet.

It conflates all sorts of events, presence, room account data, timeline, state and is just generally not helpful.
It seemingly wants to be a catch-all but doesn't include (user) account data - that's only available on the `accountData` emit

`callEventHandler` and the effects code in react-sdk's `RoomView` both listened to it instead of Room.timeline which is far more appropriate for their uses.

Can anyone see a use-case for this instead of just listening on `['User.lastPresenceTs', 'Room.timeline', 'RoomMember.typing', 'Room.receipt', 'Room.accountData']`

Maybe we should add one for `Room.ephemeralEvent` to catch ones which aren't typing/receipts for flexibility out-of-spec.

Start by examining the `event` listeners in `callEventHandler` and the effects code in react-sdk's `RoomView`, then compare their needs with `Room.timeline`. Review the listed event names and determine whether `event` has a remaining use-case or whether a `Room.ephemeralEvent` alternative is needed. Done means reaching and documenting a clear deprecation or retention decision.

Written by the indexing model from the issue text.