remove animation from overlay

[keithamus]

Description

@langermank and I were debugging as to why Overlay seems to only work properly on my devices... when we figured out that I have prefers-reduced-motion set!

In anchored-position, the following steps happen:

• IntersectionObserver is registered.
• When the user clicks the button, the element is visible.
• IntersectionObserver triggers anchored-position#update().
  • If the user has prefers-reduced-motion then no animation plays
  • If the user does not have prefers-reduced-motion then:
    • The scaleFade animation kicks in. It starts at scale(0.5) which changes the BoundingClientRect of anchored-position to be half the size.
    • The animation grows the container to scale(1)
    • The animation finishes
• A user with animations enabled observes that the position is "off" (by exactly half the width of the container element)

There are several not-ideal solutions to all of this:

• anchored-position can listen for animationend and call update(). This will have a "popping" effect as when the animation ends the element will reflow into position
• The CSS for scaleFade can add padding/margin to accommodate for the change in scale, keeping a consistent BoundingClientRect. This will be very difficult to achieve in CSS alone.
• The JS can detect if an animation is occurring via getAnimations() and if it is occuring, then call update() on each animationframe until the animation has completed. This can be very computationally expensive and may slow down animations as each frame the position will need to be recalculated
• We remove all animations and ship that (that's this PR!)
• We change to an animation style that does not change the BoundingClientRect - such as a fade-in animation.

[changeset-bot]

🦋 Changeset detected

Latest commit: 76a9642

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 1 package

Name	Type
@primer/view-components	Patch

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[keithamus]

Skipping changelog as #1401 hasn't been released yet.

[langermank]

Approving to move forward with Overlay as we can follow up with animations later! ✨