Implement copy_file_range fop for replicate volume

[pranithk]

This will enable applications on top to develop transactions on top of files, where before doing a modification, they can do a file snapshot then attempt the file operation if it is successful, keep the copy otherwise restore it from the copy. One can do it the otherway also where the file operation is done on the copy and if it is successful, then it is copied on to the original file.