Add all read-only compatible zpool features to grub2 compatibility

GRUB opens the boot pool in read-only mode. All read-only
compatible features for zpool can be enabled and added to
grub2 compatibility, as GRUB does not open the boot-pool
for write.

Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-by: Alexander Motin <mav@FreeBSD.org>
Signed-off-by: Umer Saleem <usaleem@ixsystems.com>
Closes #15459