Vulkan: Fix swap optimization after staged clear for MSAA If the MSAA image only had a clear update and the update wasn't going to be applied to the swapchain image, the clear update was accidentally dropped because `flushStagedUpdates` wouldn't see the clear update which is already extracted in `deferredClearValues`. Test: angle_end2end_tests --gtest_filter=EGLSingleBufferTest.StagedClearResolveOnSwap/* Bug: angleproject:382006939 Change-Id: I53ae26eeb8a7f38b7758f86bf97982a90b1990dd Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/6285627 Reviewed-by: Yuxin Hu <yuxinhu@google.com> Commit-Queue: Igor Nazarov <i.nazarov@samsung.com> Reviewed-by: Shahbaz Youssefi <syoussefi@chromium.org>