Add checks for FeatureFlags.QSB_ON_FIRST_SCREEN

When false, it correctly does not show the QSB but leaves
a default style search bar which cannot be removed.

Add checks to control default view visibility in device
profile layout & re-layout, QSB container and in
Workspace's onMeasure

Bug: 35967694

Change-Id: I3d0f89e1022d838eeb95762fd1fb3f7257956c41

src/com/android/launcher3/Workspace.java

@@ -643,7 +643,8 @@ public class Workspace extends PagedView
         // of workspace despite that it's not a true child.
         // Note that it relies on the strict ordering of measuring the workspace before the QSB
         // at the dragLayer level.
-        if (getChildCount() > 0) {
+        // Only measure the QSB when the view is enabled
+        if (FeatureFlags.QSB_ON_FIRST_SCREEN && getChildCount() > 0) {
             CellLayout firstPage = (CellLayout) getChildAt(0);
             int cellHeight = firstPage.getCellHeight();