Is your feature request related to a problem? Please describe.
EuiDescriptionList columns currently default to a width of 50%. Depending on the screen size, these columns can be spread quite far apart. The new prop would make this value configurable.

Describe the solution you'd like
A new columnGap prop that accepts s and m (default) as values to control the column gap. m would be the default and would be 50% (the amount used today).

Describe alternatives you've considered
The alternatives to this are kind of hacky. One such hack is using the different description list components and setting a class on DescriptionListTitle with class setting the flex-basis to the desired max width of the title column.

CC: @kyrspl