CI: add FreeBSD build with Cirrus CI

As a first step for automatic FreeBSD testing add a build and install
for FreeBSD versions 12.4, 13.2 and 14-snapshot using Cirrus CI.

Reviewed-by: Jose Luis Duran
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Martin Matuska <mm@FreeBSD.org>
Closes #15332