Vulkan: Per Context Serial cleanup. Comment in the "OutsideRenderPassCommandBufferHelper::reset()" is misleading. New "mQueueSerial" is always generated after "RendererVk::flushOutsideRPCommands()". This change removes comment and invalidates "mQueueSerial" to catch possible errors. Call "generateOutsideRenderPassCommandsQueueSerial()" in the "ContextVk::flushImpl()" only when needed. This call is necessary only with empty submission with only "signalSemaphore" and NO OutsideRP commands are written inside the "flushImpl()" (mIsAnyHostVisibleBufferWritten or mGpuEventsEnabled). Bug: b/267806287 Change-Id: Ibc547f97a6b38f70ad3d5901eca7b659b93014c0 Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/4218363 Reviewed-by: Charlie Lao <cclao@google.com> Reviewed-by: Shahbaz Youssefi <syoussefi@chromium.org> Commit-Queue: Charlie Lao <cclao@google.com>