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-upgrade.8

@@ -66,7 +66,7 @@ property).
 .Xc
 Displays legacy ZFS versions supported by the this version of ZFS.
 See
-.Xr zpool-features 5
+.Xr zpool-features 7
 for a description of feature flags features supported by this version of ZFS.
 .It Xo
 .Nm zpool
@@ -87,7 +87,7 @@ then no upgrade will take place.
 Once this is done, the pool will no longer be accessible on systems that do not
 support feature flags.
 See
-.Xr zpool-features 5
+.Xr zpool-features 7
 for details on compatibility with systems that support feature flags, but do not
 support all features enabled on the pool.
 .Bl -tag -width Ds
@@ -103,7 +103,7 @@ supported legacy version number.
 .El
 .
 .Sh SEE ALSO
-.Xr zpool-features 5 ,
-.Xr zpool-history 8 ,
-.Xr zpoolconcepts 8 ,
-.Xr zpoolprops 8
+.Xr zpool-features 7 ,
+.Xr zpoolconcepts 7 ,
+.Xr zpoolprops 7 ,
+.Xr zpool-history 8