LP#1759352: improve webstaff fix checkout specific due date UX

LP#1759352: improve webstaff fix checkout specific due date UX

The Date Options dropdown UI added as a result of bug 1717025
hides the state of the "checkboxes" for custom due date and
the datepicker wasn't disabled when custom due date was disabled.
This addresses these UX issues, to that the user has visual feedback
as to the state of that option.

Signed-off-by: Cesar Velez <cesar.velez@equinoxinitiative.org>
Signed-off-by: Rogan Hamby <rogan.hamby@gmail.com>
Signed-off-by: Galen Charlton <gmc@equinoxinitiative.org>