Parallels clone of macvm should use clonefile for disk img's if possible

APFS allows creating copy-on-write clones of files with the clonefile(2) syscall. When using prlctl clone (particularly on macvm's that don't have uncompressed disk images), it doesn't seem like there would be any downside to using this rather than a traditional copy when the host volume uses APFS and it would be massive time and space saver.