Register Instance Copies and Moves with Their Plate

An instance added with "+" was never registered with the plate it landed on,
and moving an instance only re-registered instance 0 of its object, so a copy
dragged onto another plate stayed unknown to that plate's registry. The
plate's filament list, its wipe tower preview and the position clamp all read
that registry, so a multi-filament copy moved onto a single-filament plate
drew no tower there and its tower position was never clamped.

Register new copies at creation, notify exactly the instances a move changed
(every instance of the object when one of its parts moved), and drop the
registry entry when a copy is removed again.

src/slic3r/GUI/GLCanvas3D.cpp

@@ -5059,7 +5059,21 @@ void GLCanvas3D::do_move(const std::string& snapshot_type)
     }
 
     //BBS: notify instance updates to part plater list
-    m_selection.notify_instance_update(-1, 0);
+    // Only what moved: the selected instances, or every instance of an object one of whose
+    // parts moved. Notifying a plate about an instance that stayed put invalidates its slice
+    // result, and notifying instance 0 alone left a moved copy unregistered on its new plate.
+    {
+        std::set<std::pair<int, int>> notified;
+        for (unsigned int i : m_selection.get_volume_idxs()) {
+            const GLVolume* v          = m_volumes.volumes[i];
+            const int       object_idx = v->object_idx();
+            if (object_idx < 0 || object_idx >= static_cast<int>(m_model->objects.size()))
+                continue;
+            const std::pair<int, int> key(object_idx, selection_mode == Selection::Volume ? -1 : v->instance_idx());
+            if (notified.insert(key).second)
+                m_selection.notify_instance_update(key.first, key.second);
+        }
+    }
 
     // Fixes sinking/flying instances (snaps object to buildplate)
     for (const std::pair<int, int>& i : done) {