graphics/rawtherapee: update to v5.12.

ChangeLog: https://rawtherapee.com/downloads/5.12/#new-features

I haven't touched the GCC=yes yet on the assumption it will move to
GCC 14 as default only after FreeBSD 13.4 will be out of support.

On FreeBSD 14.2, GCC 13 and 14 seem fine, assuming sufficient RAM for
MAKE_JOBS_NUMBER because C++ is quite memory hungry. In doubt, build
with a smaller MAKE_JOBS_NUMBER.