`DRW_drawdata_get` reuses the same `DrawData` for all duplis,
so they all end up using the same `ObjectHandle` and `ObjectKey`,
which breaks motion vectors.
* Don't use `DRW_drawdata_get`.
* Simplify `ObjectKey`.
This also solves the issue of objects created "on the fly" always having
the `ID_RECALC_ALL` flag.
Pull Request: https://projects.blender.org/blender/blender/pulls/112544