[lib] Generate P2P messages based on actions

Summary:
Inspired by https://phab.comm.dev/D12133. Each action can result in some messages that are defined in specs.

Depends on D12775

Test Plan: Tested in combination with the next diff. Checked if sending a DM operation results in generating P2P messages by adding some code calling a method from D12786.

Reviewers: kamil, marcin

Reviewed By: kamil

Subscribers: ashoat

Differential Revision: https://phab.comm.dev/D12776