Bug 971473 - [System2] Instantiable CallForwarding

- update bootstrap_test
- add related tests for call_forwarding
- refactor call_forwarding
Merge pull request #16772 from EragonJ/bug-971473-bubble-tea

Bug 971473 - [System2] Instantiable CallForwarding
Bug 937442 - (lockscreen-window) [Window Management] Implement LockscreenWindow to manage LockScreen