Vulkan: Feedback and testing

Hi all, The Vulkan project is getting to a state where we need to validate if it can become an official supported backend (not experimental). Last month effort was spent to make the viewport performance comparable to OpenGL. Vulkan is used to draw the user interface and EEVEE. [!NOTE] Using Vulkan as a Cycles backend is NOT a target. It will have too many limitations concerning maintainability and features. We would like feedback on stability, features not working and troublesome platforms...