Predictive back: widget to all apps

This CL adds a layer of OnBackPressedHanlderRouter to Launcher:
1. 4 OnBackPressedHandler(s) are added in such order: auto cancel action mode handler, drag handler, view handler and state handler
2. first handler who can handle back will handle the entire back gesture
3. Let WidgetsFullSheet to handle widget to all apps transition

Bug: b/260956481
Test: manual
Change-Id: Idbce3dcec746226dd68aaabaddc8fe01334e9673

src/com/android/launcher3/folder/Folder.java

@@ -1579,17 +1579,14 @@ public class Folder extends AbstractFloatingView implements ClipPathView, DragSo
         return getOpenView(activityContext, TYPE_FOLDER);
     }
 
-    /**
-     * Navigation bar back key or hardware input back key has been issued.
-     */
+    /** Navigation bar back key or hardware input back key has been issued. */
     @Override
-    public boolean onBackPressed() {
+    public void onBackInvoked() {
         if (isEditingName()) {
             mFolderName.dispatchBackKey();
         } else {
-            super.onBackPressed();
+            super.onBackInvoked();
         }
-        return true;
     }
 
     @Override