Add a config to force rounded icon for DashboardFragment.

And each page has ability to turn on/off rounded icons. This CL only
adds the flag, it doesn't actually change icon shape yet.

- Boolean config in xml
- New protected method for each DashboardFragment to load config
- Plumb the boolean into DashboardFeatureProvider for future use.
- Remove some unused APIs from DashboardFeatureProvider

Bug: 110405144
Fixes: 79748104
Test: robotests
Change-Id: Id34782e75aa7289967e4dd1f4fe2978688092702

src/com/android/settings/dashboard/DashboardAdapter.java

@@ -44,6 +44,7 @@ import com.android.settings.dashboard.conditional.Condition;
 import com.android.settings.dashboard.conditional.ConditionAdapter;
 import com.android.settings.dashboard.suggestions.SuggestionAdapter;
 import com.android.settings.overlay.FeatureFactory;
+import com.android.settings.widget.RoundedHomepageIcon;
 import com.android.settingslib.core.instrumentation.MetricsFeatureProvider;
 import com.android.settingslib.core.lifecycle.Lifecycle;
 import com.android.settingslib.core.lifecycle.LifecycleObserver;