message: Vulkan: implement insertEventMarker.
  Note that pushGroup / popGroup are already supported.
diff: @@ -1043,6 +1043,16 @@ void VulkanDriver::bindSamplers(size_t index, Handle<HwSamplerGroup> sbh) {
  }
  void VulkanDriver::insertEventMarker(char const* string, size_t len) {
  + constexpr float MARKER_COLOR[] = { 0.0f, 1.0f, 0.0f, 1.0f };
  + ASSERT_POSTCONDITION(mContext.currentCommands,
  + "Markers can only be inserted within a beginFrame / endFrame.");
  + if (mContext.debugMarkersSupported) {
  + VkDebugMarkerMarkerInfoEXT markerInfo = {};
  + markerInfo.sType = VK_STRUCTURE_TYPE_DEBUG_MARKER_MARKER_INFO_EXT;
  + memcpy(markerInfo.color, &MARKER_COLOR[0], sizeof(MARKER_COLOR));
  + markerInfo.pMarkerName = string;
  + vkCmdDebugMarkerInsertEXT(mContext.currentCommands->cmdbuffer, &markerInfo);
  + }
  }
  void VulkanDriver::pushGroupMarker(char const* string, size_t len) {
  