Fix search index for a financed device

Now with two preference controllers, one for enterprise device and one
for financed device, the search index issue (querying "Financed device
info" in Settings does not show a search result) is fixed. The financed
preference controller is used when the device is a financed device.
Otherwise, the enterprise preference controller is used.

Bug: 183551684
Test: Used a test device that is registered via ZT
Test: m RunSettingsRoboTests ROBOTEST_FILTER=EnterprisePrivacyPreferenceControllerTest
Test: m RunSettingsRoboTests ROBOTEST_FILTER=FinancedPrivacyPreferenceControllerTest
Test: m RunSettingsRoboTests ROBOTEST_FILTER=PrivacyPreferenceControllerHelperTest

Change-Id: I051144ec9004f86456285078ebb1c72266f80a55