Feature request: provide \clist_use:nn etc

[stone-zeng]

At present, LaTeX3 only has \clist_use:Nn and \clist_use:Nnnn for clist variable. Please consider to add the similar functions for explicit clist:

\clist_use:nn   { a , b , , c , {de} , f } { ~and~ }
\clist_use:nnnn { a , b , , c , {de} , f } { ~and~ } { ,~ } { ,~and~ }