cdefs: Bump the defaults for 'all'

Bump default to POSIX at 202405, C at 2023 and xopen at 800...

Sponsored by: Netflix
Reviewed by: brooks
Differential Revision: https://reviews.freebsd.org/D47578

(cherry picked from commit f95d9ec92122e6b4ef99c9a258f31b9564d327d3)