This introduce one new flag:
config_show_location_scanning
Which when set to false, will hide "Scanning" in Location preference.
Some OEMs may control Bluetooth/Wi-Fi scanning themselves, so they may
want to hide the page from users.
Bug: 62418710
Test: make RunSettingsRoboTests
ROBOTEST_FILTER=LocationScanningPreferenceControllerTest
Change-Id: I19f0020a2c94f70b3b7956529f57af098ccc79fd
