[lib] implement reply count for composable DM messages
Summary:
ENG-9273.
Depends on D13426
Test Plan:
- Reply count on sender.
- Reply count on receiver.
- Reply count when retrying.
Tested both web and native.
Reviewers: tomek, marcin
Reviewed By: tomek
Subscribers: ashoat
Differential Revision: https://phab.comm.dev/D13427