Update gesture nav colors and animation for dark/light theming

- Added light mode gesture feedback animations
- Added color resources for the fake launcher wallpaper. Also using these color resources in the feedback animations for consistency
- Using fake previous app task color in feedback animations for consistency

Bug: 169687177
Test: manual
Change-Id: I1d28212e02c2ae750ce6241b64aa90f52b827c76

quickstep/src/com/android/quickstep/interaction/HomeGestureTutorialController.java

@@ -42,8 +42,8 @@ final class HomeGestureTutorialController extends SwipeUpGestureTutorialControll
     }
 
     @Override
-    protected int getMockAppTaskThumbnailResId() {
-        return R.drawable.mock_webpage;
+    protected int getMockAppTaskThumbnailResId(boolean forDarkMode) {
+        return forDarkMode ? R.drawable.mock_webpage_dark_mode : R.drawable.mock_webpage_light_mode;
     }
 
     @Override