Vulkan: Remove mFormat from ImageHelper The only thing we need from ImageHelper::mFormat is to get intendedImageFormat. This CL simplifies the interface by simply pass in intendedImageFormat into initExternal so that ImageHelper class will not need to reference to vk::Format at all. Bug: b/196456356 Change-Id: I5fcb0d7226cae44dc865a7cfb0149d74e5756f11 Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/3111451 Commit-Queue: Charlie Lao <cclao@google.com> Reviewed-by: Jamie Madill <jmadill@chromium.org> Reviewed-by: Tim Van Patten <timvp@google.com> Reviewed-by: Shahbaz Youssefi <syoussefi@chromium.org>