Make grid-column-gutter define responsive gutters by default #8259

Resolve #8259

Make `grid-column-gutter` (and also `grid-col-gutter`) define
responsive gutters when no gutter value (`$gutter`) is given, instead
of defining gutters from the zero breakpoint.

If only a `$gutters` map is given, use this map to generate responsive
gutters.

If only a `$gutters` single value is given, use this value to generate
no-responsive gutters.