feat(styles): synced disabled and error states for select

[orest-s]

Closes: #1006

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[scurker]

I realize this file hasn't been touched in a while and has some old patterns, but our new guidelines specify these should be component level variables.

example:

:root {
  --select-background-color-disabled: var(--field-background-color-disabled)
}

.cauldron--theme-light {
  --select-background-color-disabled: /* whatever color is supposed to be here */
}

.Field__select--disabled select {
  background: var(--select-background-color-disabled);
}
...

It's okay if this takes a little more time since we're trying to align our component css patterns as well.

dismissing review, updated pr myself

[scurker]

This was done after a discussion with @dequelabs/cauldron-design in which we decided a temporary solution to address an a11y issue would be to increase the size of the focus ring upon focus.