[SettingsLib] Update "fix" shim to use new Wifi subsystem restart callbacks

Wi-Fi subsystem restart callbacks have been added to the framework.
Modify the shim to use these callbacks rather than indirectly monitor
whether the WiFi subsystem has restarted.

Bug: 175084231
Test: TBD - pending UI test integration
Change-Id: I9c127532d7cefbf2ff6612562ab46865e456b43a