Convert location settings to DashboardFragment.

- change LocationMode, LocationSettings, and ScanningSettings to be
DashboardFragment.
- remove LocationSettingsBase and moved base logics into base
controller.
- add controllers for the preferences under the 3 location settings
pages.

Fixes: 68719207
Test: make RunSettingsRoboTests
Change-Id: Icedf691c2a9f7989faebee39ea9da672209b7957