D3D11: Rename ANGLEFormatSet to Format. BUG=angleproject:1455 Change-Id: I896b3ed2d5e4ff3ad72de9a3a4b554841129e4e9 Reviewed-on: https://chromium-review.googlesource.com/367093 Reviewed-by: Geoff Lang <geofflang@chromium.org> Reviewed-by: Jamie Madill <jmadill@chromium.org> Commit-Queue: Jamie Madill <jmadill@chromium.org>