- power level content override adds to the default event instead of
replacing it
- sending code refactored to make edus possible
- remove presence events when restarting conduit
- remove room_id field from read receipts over /sync
- handle incoming read receipts
- fix array bounds bug in server_server.rs

this also reverts some stateres changes

TIL body.device_id != (*body).device_id, which is pretty bad, so I
renamed body.device_id to body.sender_device

Replace None with Some("") for state_key

Move all state event appending to append_state_pdu.

feat: first steps towards joining rooms over federation
Add state-res as a dependency of conduit
Add reverse_topological_power_sort before append_pdu
Implement statehashstatid_pduid tree for keeping track of state
Clean up implementation of state_hash as key for tracking state