[lib] factor out broadcasting device list updates to hook
Summary:
We want to reuse this code in more places, whenever disseminating device list updates.
Depends on D12347
Test Plan:
Hook tested by calling function.
Secondary device auth not tested because of: ENG-8385.
Reviewers: bartek, tomek
Reviewed By: tomek
Subscribers: ashoat
Differential Revision: https://phab.comm.dev/D12373