Improving highlight for Clear-all button.

Better shape + now has hover state.

Bug: 72222505
Test: Manual
Change-Id: I24ba55c760b15d71406a35ea5f7bf54f505741d6

quickstep/res/layout/overview_clear_all_button.xml

@@ -3,12 +3,12 @@
 <TextView
     xmlns:android="http://schemas.android.com/apk/res/android"
     android:id="@+id/clear_all_button"
+    style="@android:style/Widget.DeviceDefault.Button.Borderless"
     android:layout_width="wrap_content"
     android:layout_height="wrap_content"
     android:layout_gravity="end|top"
     android:fontFamily="sans-serif-medium"
     android:text="@string/recents_clear_all"
     android:textColor="?attr/workspaceTextColor"
-    android:background="?android:attr/selectableItemBackground"
     android:textSize="14sp"
 />

src/com/android/launcher3/PagedView.java

@@ -1556,11 +1556,6 @@ public abstract class PagedView<T extends View & PageIndicator> extends ViewGrou
         return mDownMotionY;
     }
 
-    @Override
-    public boolean onHoverEvent(android.view.MotionEvent event) {
-        return true;
-    }
-
     protected interface ComputePageScrollsLogic {
 
         boolean shouldIncludeView(View view);