Make device discoverable in Connected Devices settings page

* For fix the TreeHugger error in pi-dev, cherry pick the ag/4042235 in
  master and fix TreeHugger error. Change android.support.v7.* to androidx.*
* Set preference title by bluetooth state
* Enable bluetooth discoverable mode in Connected device page
* Add more test cases for DiscoverableFooterPreferenceController

Bug: 79294219
Test: make -j50 RunSettingsRoboTests
Change-Id: I6d4f8ec3870c43bf48e9666eabd60068aa8950bb