windowPreview: Tie icon scale to overview state

Scaling the icons all the way from/to 0 is a relatively big transition,
which is fairly distracting when playing simultaneously for multiple
previews after reaching the WINDOW_PICKER state.

Instead, tie the scale to the overview state itself, so that the animations
runs in parallel.

Part-of: <https://gitlab.gnome.org/GNOME/gnome-shell/-/merge_requests/1654>

js/ui/workspace.js

@@ -1237,7 +1237,7 @@ class Workspace extends St.Widget {
 
     // Create a clone of a (non-desktop) window and add it to the window list
     _addWindowClone(metaWindow) {
-        let clone = new WindowPreview(metaWindow, this);
+        let clone = new WindowPreview(metaWindow, this, this._overviewAdjustment);
 
         clone.connect('selected',
                       this._onCloneSelected.bind(this));