This is a big change that cleanup a lot of confusing code.
- The instancing/batching data buffer distribution in draw_instance_data.c.
- The selection & drawing code in draw_manager_exec.c
- Prety much every non-meshes object drawing (object_mode.c).
Most of the changes are just renaming but there still a chance a typo might
have sneek through.
The Batching/Instancing Shading groups are replace by DRWCallBuffers. This
is cleaner and conceptually more in line with what a DRWShadingGroup should
be.
There is still some little confusion in draw_common.c where some function
takes shgroup as input and some don't.