Improve lossless compression efficiency

The KTX v2 spec supports vanilla zlib / deflate and Zstandard schemes. On their own, they do not work well with raw pixel data, especially of floating-point formats.

One option to boost compression is to apply a lossy RDO pass to the input data. Another is to transform raw values into something more suitable for subsequent compression steps. An example of the latter is lossless PNG Filtering.

We need to design and integrate a reasonable pre-processing solution that could be used for lossless workflows.