Previously, objects and geometries were mapped between frames
using different hash tables in a way that is incompatible with
geometry instances. That is because the geometry mapping happened
without looking at the `persistent_id` of instances, which is not possible
anymore. Now, there is just one mapping that identifies the same
object at multiple points in time.
There are also two new caches for duplicated vbos and textures used for
motion blur. This data has to be duplicated, otherwise it would be freed
when another time step is evaluated. This caching existed before, but is
now a bit more explicit and works for geometry instances as well.
Differential Revision: https://developer.blender.org/D13497
4e78a7360e