Remove SkColorSpaceXformCanvas, use color-managed SkSurfaces instead

[brianosman]

No description provided.

[brianosman]

Behavior (visual) changes should be very minor. Things that are to be expected:

• A few things were not color managed correctly by the transform canvas (color emoji, some color filters). Those will be handled correctly with the tagged surfaces (although we're always transforming to sRGB, so nothing should change until we target a wider gamut).
• Image filtering will happen in the source color space, rather than the destination. Very minor.
• The transform canvas did caching of images in the destination color space. Now, the conversion happens at draw time. If there are performance issues, images can be pre-converted to the destination with makeColorSpace().

[brianosman]

The new expected PNG is visually identical, but now includes the 'sRGB' tag in the PNG header. This reflects the fact that the image being encoded has a color space attached. Previously, we produced images with a null color space, so we never included color management information in the files we encoded.