This patch will allow the user to select the EEVEE renderpass to be
shown in the viewport by default the combined pass will be shown.
Limitations:
- Viewport rendering stored the result in a RenderResult. RenderResult is not aware of the type of data it holds. So where RenderResult is used it is assumed that it stores a combined pass. The display+view transform is applied.
I will propose to fix this in a future patch. But that is still being designed and discussed.
EEVEE: Viewport Renderpasses
