c3e4cbdf changed the border of input elements to be translucent. This commit makes
input group elements and custom form inputs follow the same pattern.

Fixes #20660

Dropped `.radio-inline` and `.checkbox-inline`.

Specify `--source-map-contents true` for node-sass and `source-map-inline-sources` for clean-css.

Without this, the sourcemaps weren't found.

given `width: 100%` is always on a container now and it's constrained by max-width, we can remove our navbar changes from #21722 and #22383