Vulkan: Fix CachedPreferCoherent to actually require cached VK_MEMORY_PROPERTY_HOST_CACHED_BIT should be in requiredBits instead of preferredBits for CachedPreferCoherent buffer. This again caused pixel6 test failures. flush() call is added right after buffer allocation to fix the test failure. This likely is due to the spec says " If a range of non-coherent memory is written by the host and then invalidated without first being flushed, its contents are undefined.". Bug: b/339562049 Change-Id: Ie8529722bd03534598b03983ba447131573b1879 Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/5578276 Reviewed-by: Shahbaz Youssefi <syoussefi@chromium.org> Commit-Queue: Shahbaz Youssefi <syoussefi@chromium.org>