Add more details to the description of the fsid_guid dataset property
6333 ZFS should let the user specify or modify the fsid_guid of a dataset

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  .Sy filesystem_limit ,
  but rather imposes an additional limit. This feature must be enabled to be used
  .Po see
  .Xr zpool-features 5
  .Pc .
+ .It Sy fsid_guid Ns = Ns Sy value Ns
+ Sets the dataset fsid_guid. The fsid_guid is a 64-bit unsigned integer, used to
+ construct the vfs id when mounting a dataset.
+ This property should only be set if you need the vfs id to be identical on two
+ systems, for example in a NFS migration scenario.
+ When the fsid_guid is changed for a file system, the file system and any
+ children that inherit the mountpoint are unmounted, then remounted. If the
+ file system was shared, existing NFS clients will require a remount.
  .It Sy mountpoint Ns = Ns Pa path Ns | Ns Sy none Ns | Ns Sy legacy
  Controls the mount point used for this file system. See the
  .Sx Mount Points
  section for more information on how this property is used.
  .Pp