CHERI: add sooptcopyinptr to preserve pointer provenance

Most socket options don't involve pointers so make the default
sooptcopyin discard provenance and add a sooptcopyinptr that preserves.

Reviewed by: markj, emaste
Effort: CHERI upstreaming
Sponsored by: DARPA, AFRL, Innovate UK
Differential Revision: https://reviews.freebsd.org/D57665