Vulkan: Fix VulkanPerformanceCounterTest.SubmittingOutsideCom VulkanPerformanceCounterTest.SubmittingOutsideCommandBufferDoesNotCollectRenderPassGarbage depends on the implementation detail on how we flush and submit commands. The recent change crrev.com/c/4038095 fixes one issue that we are now having one less submission on pixel 6 device. This CL adjust the test to account for that. This CL also changed to set mHasDeferredFlush to true only when there is a started renderpass upon FBO bind. This CL also opt in swiftshader into preferSubmitAtFBOBoundary feature for test coverage and ease of debugging since ARM GPU (which enables this flag) is not been tested on CI. Bug: b/255414841 Change-Id: I295cec33a8ca257a5d5a98604b8c4c0c29e97cdf Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/4054101 Reviewed-by: Shahbaz Youssefi <syoussefi@chromium.org> Reviewed-by: Yuxin Hu <yuxinhu@google.com> Commit-Queue: Charlie Lao <cclao@google.com>