Make some existing slices public.

Only PreferenceControllers with isPublicSlice() set to true are exposed
to other apps. Others will be Settings only.

Bug: 141088937
Test: robotests
Change-Id: I5934e89bc1b268fdd44acd630621fa46987728ff

tests/robotests/src/com/android/settings/fuelgauge/SmartBatteryPreferenceControllerTest.java

@@ -120,4 +120,9 @@ public class SmartBatteryPreferenceControllerTest {
                 new SmartBatteryPreferenceController(null);
         assertThat(controller.isSliceable()).isTrue();
     }
+
+    @Test
+    public void isPublicSlice_returnsTrue() {
+        assertThat(mController.isPublicSlice()).isTrue();
+    }
 }