Remove transition on position for terminal decorations

[Tyriar]

Looks like the transition is causing the animation when scrolling the terminal:

[Tyriar]

Some other notes:

• The fatter cell-sized rectangle doesn't look great imo, thinner like SCM looks better but it seems like we'll probably move away from that.
• Using transform scale to increase the size ends up making the square a bit blurry, transitioning via width should fix that.

[meganrogge]

Going with the codicon and will do the background highlight that we do for other buttons instead of the scale transform

[rchiodo]

/verified