Add multi-thread/context test for compute shaders The "Ragnarok M: Eternal Love" game uncovered a bug where 2 contexts shared a VkCommandBuffer. The one context was used by one thread for rendering, and the other context/thread dispatched compute shaders. When the rendering thread destroyed a VkCommandBuffer, future compute dispatches crashed because the new VkCommandBuffer didn't have a compute pipeline bound. Bug: b/181711029 Change-Id: I8bc85150c1c6202e02feb84a7ccc0ad7b9c39258 Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2770681 Commit-Queue: Ian Elliott <ianelliott@google.com> Reviewed-by: Shahbaz Youssefi <syoussefi@chromium.org>