Renames all the RenderPipeline*2 stuff to simple RenderPipeline* but
keeps *2 definitionas around as typedefs and wrappers so that users can
migrate away from it.
Bug: dawn:22
Change-Id: If301d81a829bba0646c3a61068f2279932b191e0
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/51764
Commit-Queue: Brandon Jones <bajones@chromium.org>
Reviewed-by: Kai Ninomiya <kainino@chromium.org>