Replace Listbase with a VectorList for duplist generation.
Performing one heap allocation for each dupli becomes very costly on
scenes with many instances.
Using a VectorList can make playback up to 15% faster.
Most scenes will have lower performance improvements,
but none of the ones I tested were slower.
VectorLists also have the advantage of being able to query the size of
the duplilist.
Pull Request: https://projects.blender.org/blender/blender/pulls/138947
f4e6ad4d24