Include sRGB -> Linear in the cached "from sRGB" xform

This simplifies the handling of paint color conversion, as well as
GrDrawVerticesOp and the default geometry processor. We don't need
to track "linearize" separate from the color space xform. We only
supply an xform if needed. The linearize is now done automatically
by the xform, though we aren't converting to destination gamma.

https://skia-review.googlesource.com/c/skia/+/132090 will fix that.

Change-Id: I0af3f29c123c3dadb818f87c5d295bc78e2ff079
Reviewed-on: https://skia-review.googlesource.com/135141
Reviewed-by: Brian Osman <brianosman@google.com>
Commit-Queue: Brian Osman <brianosman@google.com>
7 files changed