Keep painting after cut (#13472)

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This can be enabled in Preference->Developer->Keep painted feature after
mesh change.

<img width="731" height="633" alt="init"
src="https://github.com/user-attachments/assets/8b195486-538e-4eda-9e77-bfdf1a794306"
/>


TODO:
- [ ] Bug fixes
- [ ] Make it faster
- Keep painting after other mesh operations such as reload from
disk/simplify/boolean operation etc:
  - [x] Planar cut
  - [x] Dovetail cut
  - [x] Cut with part assigned to other side
  - [x] Split to parts
  - [x] Split to objects
  - [x] Mesh boolean gizmo
  - [x] Mesh boolean in right click
- [x] Reload from disk/replace stl (won't work well if mesh changed too
much)
  - [x] Fix model
- [x] Simplify/smooth (this two won't work well due to too much mesh
changes)
- [x] Add options in settings since I think this will be experimental
for a long time until being tested by a lot of ppl

src/OrcaSlicer.cpp

@@ -4456,7 +4456,7 @@ int CLI::run(int argc, char **argv)
                 size_t num_objects = model.objects.size();
                 for (size_t i = 0; i < num_objects; ++ i) {
                     ModelObjectPtrs new_objects;
-                    model.objects.front()->split(&new_objects);
+                    model.objects.front()->split(&new_objects, false); // TODO: add cli option to enable this?
                     model.delete_object(size_t(0));
                 }
             }