[lib] broadcast updates to all peers after Secondary Device registration success

Summary:
After discussion with @bartek we concluded that after receiving SECONDARY_DEVICE_REGISTRATION_SUCCESS we should:

1. Broadcast update to all peers
2. Update our own store (we have to call getAndUpdateDeviceListsForUsers to get platform details of new device).

Depends on D12374

Test Plan: Going to test along with fixes to ENG-8385.

Reviewers: bartek, tomek

Reviewed By: bartek

Subscribers: ashoat, bartek

Differential Revision: https://phab.comm.dev/D12430