D3D11: Store more format info by-reference. This CL stores the d3d11::TextureFormat by reference in the texture storage. Adding the internalFormat to the TextureFormat allows us to store a single ref instead of three per TextureStorage11. Also store the format sets in a d3d11::TextureFormat by-ref instead of by-pointer, making the code a bit cleaner. BUG=angleproject:1455 Change-Id: I3c0e966d948c694435577d7d45dc0cd156480cdb Reviewed-on: https://chromium-review.googlesource.com/365412 Reviewed-by: Olli Etuaho <oetuaho@nvidia.com> Reviewed-by: Geoff Lang <geofflang@chromium.org> Commit-Queue: Jamie Madill <jmadill@chromium.org>