Consider: Remove display object conversions

[davesmith00000]

Indigo's render pipeline works in a few stages (waves hands), that might be:

1. Describe the scene (SceneUpdateFragment).
2. Process the scene and events.
3. Convert scene into "display objects".
4. Render.

The display objects stages is basically a simplified version of the scene graph, aimed at making rendering easier to do. It isn't strictly necessary anymore. Should it be removed?

Pro: The display object conversion is costly in terms of allocations, removing it would reduce GC pressure.

Cons:

• Removing it will be a big job.
• It's a useful abstractions layer that simplifies rendering.
• Merging the two together will create a lot more complexity and mess in the rendering code.