File copy Block cloning support

[iav]

For a while in the wild ar some system block cloning support: on local filesystem Block cloning on ReFS, on a network drive Server-Side Copy in CIFS protocol. Such support via cifs work for xfs and btrfs, and possible will be added for zfs in future. Will be good to use this option by default if it available for filesystem on file copy, with opt-out possibility.