Fix UI flicker problem and update wordings

- "Set time zone automatically" changes to "Set automatically".
- "Use location to set time zone" changes to "Use location"
- Add a new summary text with "Location may be used to set time zone".

Fixes: 233968737
Test: make RunSettingsRoboTests -j ROBOTEST_FILTER=com.android.settings.datetime
Change-Id: Ia16c428e906cda4ebe052bad83c3f574075a7a64

tests/robotests/src/com/android/settings/datetime/LocationTimeZoneDetectionPreferenceControllerTest.java

@@ -150,7 +150,8 @@ public class LocationTimeZoneDetectionPreferenceControllerTest {
                 new TimeZoneCapabilitiesAndConfig(capabilities, configuration);
 
         when(mTimeManager.getTimeZoneCapabilitiesAndConfig()).thenReturn(capabilitiesAndConfig);
-        assertThat(mController.getSummary().toString()).isEmpty();
+        assertThat(mController.getSummary()).isEqualTo(
+                mContext.getString(R.string.location_time_zone_detection_auto_is_on));
     }
 
     @Test