Vulkan: Enable async pipeline cache sync by default Bug: b/246683126 Change-Id: I593650364250f8802e9f546ab9957cf1c30e596a Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/4031487 Reviewed-by: Cody Northrop <cnorthrop@google.com> Commit-Queue: Shahbaz Youssefi <syoussefi@chromium.org>