Add isSliceable API to BasePrefController

Only support explicitly approved Settings Slices,
dictated by controllers which return true for the new
method isSliceable.

Updating the supported settings to a whitelist means that
the method to return all available slices must be updated,
and checking slicability when we index slices.

Test: robotests
Bug: 79779103
Change-Id: Ib2b9690cdd0036b5cc4a1cb846c52bce7c824ab9

src/com/android/settings/display/AutoRotatePreferenceController.java

@@ -15,6 +15,7 @@ package com.android.settings.display;
 
 import android.content.Context;
 import androidx.preference.Preference;
+import android.text.TextUtils;
 
 import com.android.internal.logging.nano.MetricsProto;
 import com.android.internal.view.RotationPolicy;
@@ -71,7 +72,12 @@ public class AutoRotatePreferenceController extends TogglePreferenceController i
     @Override
     public int getAvailabilityStatus() {
         return RotationPolicy.isRotationLockToggleVisible(mContext)
-                ? AVAILABLE : CONDITIONALLY_UNAVAILABLE;
+                ? AVAILABLE : UNSUPPORTED_ON_DEVICE;
+    }
+
+    @Override
+    public boolean isSliceable() {
+        return TextUtils.equals(getPreferenceKey(), "auto_rotate");
     }
 
     @Override