Refactor of SkColorSpaceXformOpts

(1) Performance is better or stays the same.

(2) Code is split into functions (RasterPipeline-ish
    design).  IMO, it's not really more or less readable.
    But I think it's now much easier add capabilities,
    apply optimizations, or do more refactors.  Or to
    actually use RasterPipeline.  I help back from trying
    any of these to try to keep this CL sane.

BUG=skia:
GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=2194303002
CQ_INCLUDE_TRYBOTS=master.client.skia:Test-Ubuntu-GCC-GCE-CPU-AVX2-x86_64-Release-SKNX_NO_SIMD-Trybot

Review-Url: https://codereview.chromium.org/2194303002
8 files changed