No more tweener

[jeffchannell]

PR fixes 1, 3, and half of 4 from latest rejection:

1. Tweener is a deprecated module. Please remove it for the next version. You can use ease() instead (supported on 3.36 and higher). For example:

   widget.ease({    
       x: newX,
       y: 10,
       opacity: 100,
       duration: 2000,
       mode: Clutter.AnimationMode.EASE_OUT_BOUNCE,
       onComplete: () => {
           log('Animation is finished');
       }
   });

   More about animation mode: https://gjs-docs.gnome.org/clutter10~10_api/clutter.animationmode

2. Don't create objects in global scope (line 130 prefs.js). Create gsettings object inside PrefsWidget.

3. What's the reason for disabling extension in init? (line 113 extension.js). You shouldn't need that.

4. enable and disable function shouldn't throw like that. Please remove those try catch block.

5. Where do you remove those timeouts you are adding in enable? https://gjs.guide/extensions/review-guidelines/review-guidelines.html#remove-main-loop-sources

[jeffchannell]

I ran into issues using ease, since neither of the places Tweener was used accessed properties that were able to be animated with Clutter.