Support contextual suggestion

- add a suggestion layout
- add an interface to get fragment in suggestion feature provider
- remove the first preference category of homepage IA to align its top
  with the bottom of the search box

Bug: 173768418
Test: robotest
Change-Id: I784e3eef29ca474c4c89f07b916c6500fabbf7d4

src/com/android/settings/dashboard/suggestions/SuggestionFeatureProvider.java

@@ -21,6 +21,7 @@ import android.content.Context;
 import android.content.SharedPreferences;
 
 import androidx.annotation.NonNull;
+import androidx.fragment.app.Fragment;
 
 /** Interface should be implemented if you have added new suggestions */
 public interface SuggestionFeatureProvider {
@@ -42,4 +43,9 @@ public interface SuggestionFeatureProvider {
      * Returns the {@link SharedPreferences} that holds metadata for suggestions.
      */
     SharedPreferences getSharedPrefs(Context context);
+
+    /**
+     * Returns the class of {@link Fragment} that supports contextual suggestion.
+     */
+    Class<? extends Fragment> getContextualSuggestionFragment();
 }

src/com/android/settings/dashboard/suggestions/SuggestionFeatureProviderImpl.java

@@ -22,6 +22,7 @@ import android.content.Context;
 import android.content.SharedPreferences;
 
 import androidx.annotation.NonNull;
+import androidx.fragment.app.Fragment;
 
 import com.android.settings.Settings.NightDisplaySuggestionActivity;
 import com.android.settings.biometrics.fingerprint.FingerprintEnrollSuggestionActivity;
@@ -86,6 +87,11 @@ public class SuggestionFeatureProviderImpl implements SuggestionFeatureProvider
         return context.getSharedPreferences(SHARED_PREF_FILENAME, Context.MODE_PRIVATE);
     }
 
+    @Override
+    public Class<? extends Fragment> getContextualSuggestionFragment() {
+        return null;
+    }
+
     public SuggestionFeatureProviderImpl(Context context) {
         final Context appContext = context.getApplicationContext();
         mMetricsFeatureProvider = FeatureFactory.getFactory(appContext)