security/vuxml: Add SA_ID to make newentry

Automate registration of FreeBSD Security Advisories.

It adds a new parameter for the newentry subcommand accepting a SA ID as present
in the FreeBSD Security Advisories web page
(https://www.freebsd.org/security/advisories/)

Fills an entry following the common structure for FreeBSD SAs and leaves some
"FIXME" strings in those places that need special care.
Developers should NOT blindly trust the output of the script.

make newentry SA_ID=FreeBSD-SA-23:11.wifi.asc
make newentry SA_ID=FreeBSD-SA-22:01.vt

Reviewed by: philip@
Differential Revision: https://reviews.freebsd.org/D41966