Add example LUT/CTF files for doing performance tuning

Under tests/data/files there are already a lot of example LUTs in many formats. However, these are mostly used for LUT file format parser tests. It would be useful to have some LUTs that are specifically recommended for performance tuning. It would be helpful to add to the documentation in the contributor guide recommending a specific set of files to use.

The existing files already contain examples of single operators but it would be helpful to have more examples of files, in CLF or CTF format, that contain multiple operators, since this more representative of a complex transform.

One file that is a useful example of a transform that uses many different operators is the heavy_transform_tetra.ctf file that was uploaded in to Slack recently:
https://opencolorio.slack.com/files/U3R43KX3N/F05T30VE6G1/heavy_transform_tetra.clf.zip

まず、tests/data/files 配下の既存の例とコントリビューターガイドを確認します。issue にリンクされている heavy_transform_tetra.ctf のリファレンスを調査し、その後、パフォーマンスチューニングに適した複数オペレーターの CLF または CTF の例を特定します。推奨ファイルが追加され、コントリビューターガイドにどのセットを使用するかが説明されていれば完了です。

索引モデルが issue の本文から書いたものです。