HPCC-9218 - Further DFS refactoring solving some superfile issues

Remove/Add sequence of same file resolved properly (see HPCC-9202),
(restore check in prepare())
Renaming files then adding them to super resolved.
Renaming merge to existing file on another cluster resolved.
Renaming split from existing file on multiple clusters resolved.

Signed-off-by: Jake Smith <jake.smith@lexisnexis.com>