assets: fix deepcopy of webassets.filter.options

• FIX Implements __deepcopy__ method for webassets.filter.option in order to fix unexpected behavior of the option class contructor. (addresses #2777) (fixes #2864) (closes #2921)

Reviewed-by: Javier Martin <javier.martin.montull@cern.ch>
Signed-off-by: Jiri Kuncar <jiri.kuncar@cern.ch>