[SS 4.4] Bootstrap 4.3 form validation state indicators are misaligned

[robbieaverill]

Version: SS 4.4.x-dev

With Bootstrap 4.3 the new form field validation states come with visual indicators as background positions, but they're slightly out of alignment in the CMS:

That example is also buggy because it's showing the X over the browser's native dropdown caret. The Bootstrap docs have an example of what dropdowns should look like in validation states: https://getbootstrap.com/docs/4.3/components/forms/#supported-elements

Text fields are a better example:

Bootstrap recommends "using custom validation styles, as native browser default validation messages are not consistently exposed to assistive technologies in all browsers (most notably, Chrome on desktop and mobile).".

https://getbootstrap.com/docs/4.3/components/forms/#custom-styles

We may also want to remove the icon indicators.