[6.x] Make the stack hover effect a little less twitchy

[JayGeorge]

Description of the Problem

When there are a few stacks on top of each other, if you hover on the lower stacks, you see them "peek out".
This is great, but I found the movement a little bit twitchy at 150ms.

Conversely, other stack movements were at 250ms with the default ease, which felt a little sluggish.

What this PR Does

• Makes the stack hover effect a little less twitchy by increasing the duration by 50ms so the animation doesn't jolt.
• Shifting other stack movements to use ease-out, which feels more responsive (immediate start and natural deceleration), and reducing them to 200ms like the other stack movement.
• Adds will-change to some of these stack elements. We're moving large panels here, and I found will-change felt snappier, hinting to the browser how the element is expected to change.

How to Reproduce

1. Edit a blueprint and add a Bard, then configure a set to see a few stacks on top of each other
2. Hover over the existing stacks and also close the stacks, to get a feel of how things fall back into place