Consistentify miscellaneous style on remaining manpages

Most notably this fixes the vdev_id(8) non-.Xrs in vdev_id.conf.5

Reviewed-by: Richard Laager <rlaager@wiktel.com>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Ahelenia Ziemiańska <nabijaczleweli@nabijaczleweli.xyz>
Closes #12212