Vulkan: Get rid of level layer "storage" views. By using a 2D instead of 2D array view for the render target we can merge the 'storage' and 'draw' level/layer views. Bug: angleproject:3975 Change-Id: Icf8c0bf6bec4147595c2b728362abd51bdf03f3e Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/1841947 Reviewed-by: Courtney Goeltzenleuchter <courtneygo@google.com> Reviewed-by: Cody Northrop <cnorthrop@google.com> Commit-Queue: Jamie Madill <jmadill@chromium.org>