[lib] Process DMOperations when received from peers via Tunnelbroker

Summary:
This is part of addressing ENG-8425.

I'll submit a follow-up diff that introduces a new action here to process the resultant data we receive.

Submitting this now so @tomek can see the code, as his work relates to this code.

Test Plan: Test plan described here

Reviewers: tomek, kamil, marcin

Reviewed By: tomek

Subscribers: tomek

Differential Revision: https://phab.comm.dev/D12741