automation/cirrus-ci: introduce FreeBSD randconfig builds

automation/cirrus-ci: introduce FreeBSD randconfig builds

Add a new randconfig job for each FreeBSD version.  This requires some
rework of the template so common parts can be shared between the full and
the randconfig builds.  Such randconfig builds are relevant because FreeBSD
is the only tested system that has a full non-GNU toolchain.

While there replace the usage of the python311 package with python3, which is
already using 3.11, and remove the install of the plain python package for full
builds.

Signed-off-by: Roger Pau Monné <roger.pau@citrix.com>
Reviewed-by: Andrew Cooper <andrew.cooper3@citrix.com>
Release-Acked-by: Oleksii Kurochko<oleksii.kurochko@gmail.com>