[lib] resend messages after race condition

Summary:
ENG-6982

ENG-7038

Depends on D13031

Test Plan:

1. Create a session between devices A and B
2. On B comment out sending confirmation.
3. Send some messages from A to B
4. From B to A send a session request with the same session counter to trigger resolving the race condition
5. Test that all messages are sent again and decrypted successfully

Reviewers: tomek

Reviewed By: tomek

Subscribers: ashoat

Differential Revision: https://phab.comm.dev/D13032