Hide taskbar icons when recents button is disabled

The idea is that both taskbar icons and recents navigate you to new apps, which we'd want to disable in similar contexts. Hence reusing FLAG_DISABLE_RECENTS.

Test: locally set FLAG_DISABLE_RECENTS=true, ensure taskbar icons don't show up (both in 3 button mode and gesture nav)
Bug: 193183428
Bug: 194990283
Change-Id: I9537f57dc25663151b1414c5260dadb58506fdb0

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

@@ -260,6 +260,13 @@ public class NavbarButtonsViewController {
         return (mState & FLAG_IME_VISIBLE) != 0;
     }
 
+    /**
+     * Returns true if the recents (overview) button is disabled
+     */
+    public boolean isRecentsDisabled() {
+        return (mState & FLAG_DISABLE_RECENTS) != 0;
+    }
+
     /**
      * Adds the bounds corresponding to all visible buttons to provided region
      */