FreeBSD: Implement hole-punching support

This adds supports for hole-punching facilities in the FreeBSD kernel
starting from __FreeBSD_version 1400032.

Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-by: Alexander Motin <mav@FreeBSD.org>
Reviewed-by: Ryan Moeller <ryan@iXsystems.com>
Signed-off-by: Ka Ho Ng <khng@FreeBSD.org>
Sponsored-by: The FreeBSD Foundation
Closes #12458