- disabled opacity is fairly static and can be DRYed out

- loading spinner: no styles being applied so this isn't necessary

+ remove passed `layout` arg in favor of static definitions

- rewrite vertical vs horizontal gutters utils to be slightly less confusing

+ replace `calc()` with `mathWithUnits()`

+ prefer inline JSX

+ rerun VRT to confirm no regressions. changes are minute/from font aliasing

- replace `EuiHideFor/ShowFor` usage with a breakpoint hook instead

+ remove unnecessary fragments

+ remove some unnecessary callback consts, just inline them if they're not reused and we're not going to memoize them

- `list_group_item` has too much conditional JSX to deal with right now, should likely be split up into subcomponents in the future

+ remove unnecessary style functions, just use a static obj instead

+ re-run VRT screenshots

+ reduce # of style fns for horizontal steps, and remove unnecessary onClick fn in favor of just inlining it (if we're not reusing or memoizing it)

+ update VRT

- instead of another div and repeated CSS, just use `> *` (which has zero specificity and is very overrideable) to bump the icon/avatar above the vertical line

+ inline `iconRender` and `ariaLabel`, it's not reused and not particularly increasing readability by being a const