Code Quality: Refactor Copy and Move collision processing

[KrisVandermotten]

Resolved / Related Issues

• Closes Code Quality: Copy and Move collision processing can be improved #18210

Steps used to test these changes

1. Open Files
2. Select a set of files or folders.
3. Copy them into some other folder.
4. Select a subset of those same files or folders.
5. Copy them again into the same folder.
6. Observe that you are asked to resolve the correct set of conflicts.
7. Observe that your chosen conflict resolution methods are honored.
8. Move some of the copied files or folders back into the source folder.
9. Observe that you are asked to resolve the correct set of conflicts.
10. Observe that your chosen conflict resolution methods are honored.
11. Undo your changes.

[hishitetsu]

It looks like a good performance improvement, and I don't see any problems. LGTM

[yair100]

@hishitetsu thank you for reviewing.