security/cyrus-sasl2-xoauth2: New port

This is a plugin implementation of XOAUTH2 for cyrus-sasl2.

WWW: https://github.com/moriyoshi/cyrus-sasl-xoauth2/
PR: 252676
Sponsored by: The FreeBSD Foundation

Co-authored-by: Thierry Dussuet <thierry.dussuet@protonmail.com>