plugins/overview: Adds a border around hovered and selected desktop in desktopGrid

Currently desktop grid view is missing the selection rectangle when hovered over a desktop.
This adds the selection rectangle on hover, since it used to be there before three-state design.

Currently selected desktop has thinner and different colored border.


![image](/uploads/ad1f2f7acbe602fb7b9479ce859026b7/image.png)

![image](/uploads/9fa50bac4b81958da0b8926f8d2518ba/image.png)

![image](/uploads/3e46c1f5a740c40bbf18a5d887f31d39/image.png)

BUG:481812


(cherry picked from commit 181ce590)

9b22e56c Adds a border around hovered desktop in desktopGrid
0566df70 Simplify code
f4a4fd4c Use different color and spacing for already selected desktop
99a7fc51 Show borders only in desktop grid view
6c12f24a fix indent
a8981c94 Add parenthesis to ternary expressions, remove stray line
075b6117 Apply 1 suggestion(s) to 1 file(s)