Change screensaver ctrlr to base pref ctrlr.

This change makes it that the ScreenSaverPreferenceController extends
BasePreferenceController so that it can be readily used and pointed to
from an xml file.

Bug: 261627295
Test: atest ScreenSaverPreferenceControllerTest

Change-Id: I95487f2f49a23422fff46f30b0cfa287582a547b
4 files changed