plugins/overview: close when double-clicking on a desktop

Now that a single-click on a desktop in the desktop bar switches Virtual
Desktops within the Overview effect, it would be nice to have an easy way
to also trigger the prior behavior of switching and also closing the effect.

This can be accomplished by letting people double-click on a desktop to
both switch to it and also close the effect.

I found myself doing this automatically; IMO it feels quite natural.

BUG: 469307
FIXED-IN: 6.0

@teams/usability