[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