Restrict screen saver settings searches to enabled users.

If a user can't enable screen saver, they shouldn't be able to
accidentally find screen saver related settings in Settings.

Bug: 260276394
Test: atest ScreenSaverPreferenceControllerTest
Test: manually by settings up a second user on a device that supports
screen saver, switching to that user, and making sure that searches for
"screen saver" don't accidentally reveal settings that can't be
accessed.

Merged-In: If2f465b2acb548455f0868507cf47217ea1a626f
Change-Id: I96fb8f9c6c4960f203b51bb43994f7bafdcefdf5