- Use the syntactic wrap/unwrap method to make code more readable.
- Update comment about hidden struct behind opaque types.
- Cleanup GPUDrawList type.
This is in preparation of vulkan backend. We move all opengl
functionnalities behind an abstract class.
This also cleansup the "dynamic" ubo create and rename it to
`GPU_uniformbuf_from_list()`
Contains, no functional change.
Part of T68990 Vulkan support.