[EuiFormControlLayout] Consider options for moving style overrides out of this layout component

[ryankeairns]

eui/src/components/form/form_control_layout/_form_control_layout.scss

Line 71 in 8d95c81

background-color: $euiFormInputGroupLabelBackground;

(At the time of writing, this was 1 of five instance of background-color overrides in this file.)

The visual style overrides in this component can result in some unintentional cascading effects. From a purest standpoint, this component is also layout-oriented, by definition, and probably ought not be concerned with visual styles to the degree possible. From a historical perspective, these overrides appear to have come into play during the Amsterdam theme creation when dealing with setting focus state designs.

As we progress through Emotion conversions this has become more evident with buttons being converted before the form layout components, for example.