Move properties, parameters, events, and concepts around manual sections

The pages moved as follows:
  zpool-features.{5 => 7}
  spl{-module-parameters.5 => .4}
  zfs{-module-parameters.5 => .4}
  zfs-events.5 => into zpool-events.8
  zfsconcepts.{8 => 7}
  zfsprops.{8 => 7}
  zpoolconcepts.{8 => 7}
  zpoolprops.{8 => 7}

Reviewed-by: Richard Laager <rlaager@wiktel.com>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Ahelenia Ziemiańska <nabijaczleweli@nabijaczleweli.xyz>
Co-authored-by: Daniel Ebdrup Jensen <debdrup@FreeBSD.org>
Closes #12149
Closes #12212

man/man8/zpool-get.8

@@ -76,7 +76,7 @@ Property source, either
 .El
 .Pp
 See the
-.Xr zpoolprops 8
+.Xr zpoolprops 7
 manual page for more information on the available pool properties.
 .Bl -tag -compact -offset Ds -width "-o field"
 .It Fl H
@@ -97,12 +97,12 @@ Display numbers in parsable (exact) values.
 .Xc
 Sets the given property on the specified pool.
 See the
-.Xr zpoolprops 8
+.Xr zpoolprops 7
 manual page for more information on what properties can be set and acceptable
 values.
 .El
 .
 .Sh SEE ALSO
-.Xr zpool-features 5 ,
-.Xr zpool-list 8 ,
-.Xr zpoolprops 8
+.Xr zpool-features 7 ,
+.Xr zpoolprops 7 ,
+.Xr zpool-list 8