D3D11: Move texture format code out of the python script. It's better to maintain the code outside of a generator script. It gives easier formatting and updating. BUG=angleproject:1455 Change-Id: I2b4383f1ed01545004de10024d03879201e2bf41 Reviewed-on: https://chromium-review.googlesource.com/365410 Reviewed-by: Corentin Wallez <cwallez@chromium.org> Commit-Queue: Jamie Madill <jmadill@chromium.org>