Fixing test that fail when FOLDABLE_SINGLE_PAGE is set to true

We need to change the result of REQUEST_IS_TWO_PANELS when the
flag is on because now we don't have two panels only 1.

Another of the issues is a rounding error when calling
getUnusedHorizontalSpace().

And lastly updating workspaceToBoards so that it maps the coordinate
of workspace items to their right position.

Bug: 270395274
Test: atest ReorderWidgets
Change-Id: I2620e5bf1ba132f984e00d2a6c21081953d259fd

src/com/android/launcher3/MultipageCellLayout.java

@@ -94,6 +94,13 @@ public class MultipageCellLayout extends CellLayout {
         }
     }
 
+    @Override
+    public int getUnusedHorizontalSpace() {
+        return (int) Math.ceil(
+                (getMeasuredWidth() - getPaddingLeft() - getPaddingRight() - (mCountX * mCellWidth)
+                        - ((mCountX - 1) * mBorderSpace.x)) / 2f);
+    }
+
     @Override
     protected void onDraw(Canvas canvas) {
         if (mLeftBackground.getAlpha() > 0) {