All meshes put through a spline share the same id on the instance segmentation

[jorge-kabuto]

Due to changes in how the spline meshes are rendered, after the change to 5.5 the meshes placed through a spline share the same UniqueID on the Instance Segmentation view.

This could be fixed by either truncating further the UniqueID for these actors, encoding the instance number on the ID directly, or by extending the information being rendered to support the extra information.

The relevant code is found on the file Tagger.cpp line 77