Add bluetooth discoverable footer preference in connected devices page

* For fix the TreeHugger error in pi-dev, cherry pick the ag/4042014 in
  master and fix TreeHugger error. Change android.support.v7.* to androidx.*
* Dynamicly add preference in controller
* Add test cases for DiscoverableFooterPreferenceController

Bug: 79294219
Test: make -j50 RunSettingsRoboTests
Change-Id: Id4c1e86c9a0a0cd69d8106a18f2cf4a0fa31782b