Make sure the task bar stays unstashed upon configuration change

So we recreate task bars when configuration is changed, if ENABLE_TASKBAR_NAVBAR_UNIFICATION = true. In order for unstashed state to propagate, we need to save STASHED_IN_APP_AUTO in TaskbarSharedState.

Fixes: 311429718
Test: Unstash the task bar in app, rotate, make sure the task bar stays unstashed
Change-Id: I7db773725ea89976612e9e91af5b6911d0ec5fc0

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

@@ -86,4 +86,8 @@ public class TaskbarSharedState {
     public void setTaskbarWasPinned(boolean taskbarWasPinned) {
         mTaskbarWasPinned = taskbarWasPinned;
     }
+
+    // To track if taskbar was stashed / unstashed between configuration changes (which recreates
+    // the task bar).
+    public Boolean taskbarWasStashedAuto = true;
 }