nfsv42: initial support for intra-server copy

Motivation:
the newer libc make use of copy_file_range function, that directly
mapped to NFSv4.2 COPY request.

Modification:
Add initial implementation on OperationCOPY that synchronously copies
the data between two open files.

Result:
initial step to support intra-server copy.

Acked-by: Paul Millar
Target: master
1 job for master in 1 minute and 37 seconds (queued for 4 seconds)
Status Name Job ID Coverage
  Build
passed build #35328

00:01:37