[lib] refactor sending OutboundP2PMessages to peers
Summary:
ENG-9106.
New approach, in linked task there is documented what changes and why this is better.
Depends on D13374
Test Plan:
- Test sending messages when session not exists.
- Test sending when session exists.
- Make sure notifs still works.
Reviewers: bartek, tomek, marcin
Reviewed By: bartek, tomek
Subscribers: ashoat
Differential Revision: https://phab.comm.dev/D13376