Revert of Move sRGB <-> linear conversion components to their own files. (patchset #5 id:80001 of https://codereview.chromium.org/2128893002/ )

Reason for revert:
Monotonicity assert is failing on ARM.  (Different rsqrt() and invert() precision?)  Will investigate a bit tomorrow... might reland with the test TODO.

Original issue's description:
> Move sRGB <-> linear conversion components to their own files.
>
> This makes them a little easier to use outside SkColorXform code.
>
> I've added some notes about how best to use them and their eccentricities, and added a test.
>
> Ultimately any software sRGB <-> linear conversion should funnel somehow through here.
>
> BUG=skia:
> GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=2128893002
> CQ_EXTRA_TRYBOTS=client.skia:Test-Ubuntu-GCC-GCE-CPU-AVX2-x86_64-Release-SKNX_NO_SIMD-Trybot
>
> Committed: https://skia.googlesource.com/skia/+/45e58c8807179638980aae8503573b950b844e4c

TBR=reed@google.com,msarett@google.com,mtklein@chromium.org
# Skipping CQ checks because original CL landed less than 1 days ago.
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=skia:

Review-Url: https://codereview.chromium.org/2131793002
6 files changed