Create a list model for read markers. The primary reason is to stop `RoomMembers` being accessed after their state event is deleted. With this the read marker doesn't pass and `RoomMember` objects to qml.
Depends on https://github.com/quotient-im/libQuotient/pull/695
Currently basic just to show a working implementation using RoomMember. Currently only the room event and search models are moved over. Will change everything else over once the dependent pr is complete.
There are 2 main reason for doing this:
1. Because I can, I wanted to see if I could do it
2. It gets rid of the janky qml re parenting stuff so should be faster.
