drs_utils: Add infrastructure to support 'clone with rename'

drs_utils: Add infrastructure to support 'clone with rename'

Our end goal is to create a backup clone of a DB, but rename the
domain/realm so we can startup the backup DC without interferring with
the existing Samba network. The basic strategy to do this is to leverage
DRS replication - by renaming the first object in the partition, all
subsequent objects will automatically be renamed.

This patch adds the infrastructure to do this. I've used object
inheritance to handle the special case of renaming the partition
objects. This means the domain-rename special case doesn't really
pollute the existing DRS replication code. All it needs is a small
refactor to create a new 'process_chunk()' function that the new
sub-class can then override.

Signed-off-by: Tim Beale <timbeale@catalyst.net.nz>
Reviewed-by: Andrew Bartlett <abartlet@samba.org>
Reviewed-by: Gary Lockyer <gary@catalyst.net.nz>