- doesn't need to live in the main form vars fn, these variables are very specific to these components

- simplify `customControlDisabledIconColor` to just darkShade - it's close enough and doesn't require extra computation

- more future proof for icon changes and generally less CSS

- extra DOM is worth it, IMO

- remove old Emotion mixin, I'm makin' my own

- note the different DOM rendering - now that we have `:has` CSS, we don't need to rely on flat `+` selectors

- prefer flex for center alignment over absolute positioning

- literally just needs `border-radius: 50%` instead

+ inline conditional label

- remove `--noLabel` modifier (replaced with `:has` CSS)

- inline conditional label, remove need for useMemo

- inline the border-radius, it's only used here and doesn't need to be a shared var (it technically already is one)

+ misc cleanup while here - fragment syntax, test syntax

- a lot of colors are being simplified and slightly tweaked here to reduce transparency as well as one-off tinting/shading

- remove Sass vars

- remove unnecessary min-height

- not sure if this is worth it, may revert

- move thumb to outside body since it has `overflow: hidden` and we want thumbs to be able to scale outside

- use `aspect-ratio` CSS instead of static width/height that changes (instead inherits from the button which is already sized)

- simplify `-1px` shenanigans by reducing transforms by default, store in thumbScales var
+ tweak hover/active states accordingly and DRY out a util for it

- simplify DOM
- rename `__track` to `__icons`, feels more accurate

- prefer flex and padding to center/position icons instead of positioning

- no need for border-radius, `__body` already has it set + overflow hidden

+ update VRT to be more useful for permutation testing

+ fix broken EuiDataGrid drag/drop behavior - we can't use the scroll shadow transform Z workaround and drag/drop at the same time 🫠

- will no longer be a thing once the EuiFormRow PR merges, drop this commit then

- Chrome/Edge's auto style defaults to currentColor which is the empty shade, so its invisible

- Safari's is just godawful