Adds transient props notation where necessary to prevent non HTML props
from leaking to the DOM.

The `animate` prop of the spinner component was previously named as
`disableAnimation`, and probably during rename, its logic wasn't
inverted. So this commit adjusts the logic and animate has the correct
and expected behavior.

Ensures that the button has accessibility tags by indicating the label
tag in stacked layout via `aria-labelledBy` attribute.
Additionaly, corrects a malformed css style that caused the stacked
layout button to render its icons out of place when `helperOnClick` prop
is specified.