Add task menu item to move task to Desktop

- Call SystemUiProxy.moveToDesktop to move existing Overview tasks to desktop
- Animation polish will be handled separately
- Refactored AbstractFloatingView method into a helper to allow testing

Fix: 320310347
Test: DesktopSystemShortcutTest, AbstractFloatingViewHelperTest
Flag: ACONFIG com.android.window.flags.enable_desktop_windowing_mode DEVELOPMENT
Change-Id: I2e4e04182e46ba4750e0683ee1789ba8fada06ea

src/com/android/launcher3/AbstractFloatingView.java

@@ -278,18 +278,7 @@ public abstract class AbstractFloatingView extends LinearLayout implements Touch
 
     public static void closeOpenViews(ActivityContext activity, boolean animate,
             @FloatingViewType int type) {
-        BaseDragLayer dragLayer = activity.getDragLayer();
-        // Iterate in reverse order. AbstractFloatingView is added later to the dragLayer,
-        // and will be one of the last views.
-        for (int i = dragLayer.getChildCount() - 1; i >= 0; i--) {
-            View child = dragLayer.getChildAt(i);
-            if (child instanceof AbstractFloatingView) {
-                AbstractFloatingView abs = (AbstractFloatingView) child;
-                if (abs.isOfType(type)) {
-                    abs.close(animate);
-                }
-            }
-        }
+        new AbstractFloatingViewHelper().closeOpenViews(activity, animate, type);
     }
 
     public static void closeAllOpenViews(ActivityContext activity, boolean animate) {