Cuda use streams and async to avoid busywaiting
Cuda use streams and async to avoid busywaiting

This switches api usage for cuda towards using more of the Async calls.

Updating only once every second is sufficiently cheap that I don't think it is worth doing it less often.

Reviewed By: brecht

Differential Revision: https://developer.blender.org/D262

pyrochlore/cycles,tangent-opensource/coreBlackbird,pyrochlore/cycles,tangent-opensource/coreBlackbird,tangent-opensource/coreBlackbird,pyrochlore/cycles