This add a new set of (possible) render settings that can be defined at
the scene level and overridable at the scene layer level.
Once we get workspaces we can either add workspace inbetween scene and
scene layer evaluation. Or to replace layer settings, to avoid extra
confusion to users.
An example of this setting is "samples", as implemented now for the clay
engine.
This can be used by any engine actually. For example to give feedback
regarding probe caching in Eevee, ....
Unline master, we try to conciliate both the original viewport info
(FPS, view name) and the render info.
Note: I had to split the function in two because the camera alpha
passepartout is handled inside the view3d_draw_region_info function.
Review: Campbell Barton and Clement Foucault.
Thanks to Sergey Sharybin and Pablo Vazquez for some of the design
discussions.
8b2640f08 introduced the error,
caused by external-engine needing depth mask to be disabled,
which happened to be the case before changing state changing logic.
We can now use object and other modes on top of Cycles.
Since we are now always on "render_to_view" (old Rendered mode), the
pause button is always visible.