[App list] improve the behavior when there is multiple windows opened for an icon

[wiiznokes]

Gnome have this interesting behavior that i think is better than the current little overview.

As you see, there is two instance of terminal

And this is what happen when we click on the terminal icon

[git-f0x]

Not sure how something similar to the above would be done in COSMIC.
But the behavior described in pop-os/cosmic-epoch#293 would be a nice improvement.