Creates BubbleStashController & BubbleStashedHandleViewController

Adds two controllers to manage and animate the stash / unstash state
of the bubble bar. Adds them to BubbleControllers.

Bug: 253318833
Test: manual, with other CLs, see go/bubble-bar-tests
Flag: WM_BUBBLE_BAR
Change-Id: I1a67da888384b1ae0fe3f79a25ea6a2c1b7eef87

quickstep/src/com/android/launcher3/taskbar/StashedHandleView.java

@@ -30,6 +30,10 @@ import androidx.core.content.ContextCompat;
 import com.android.launcher3.LauncherAnimUtils;
 import com.android.launcher3.R;
 
+/**
+ * View to render a handle that changes color based on the background to ensure contrast. Used for
+ * the taskbar when stashed as well as the bubble bar when stashed.
+ */
 public class StashedHandleView extends View {
 
     private static final long COLOR_CHANGE_DURATION = 120;