Add SkEncodedInfo to report properties of encoded image data

All this does is build an SkEncodedInfo for each codec, and
then convert it to an SkImageInfo.

In future steps I intend to:
(1) Use SkEncodedInfo in place of SrcConfig in SkSwizzler.
(2) Support more conversions in SkSwizzler (non-native
BGRA/RGBA, 16-bit components, float, fixed point)
(3) Investigate optimizing conversions from encoded data
to linear color spaces.

BUG=skia:4133
GOLD_TRYBOT_URL= https://gold.skia.org/search2?unt=true&query=source_type%3Dgm&master=false&issue=1820073002

Review URL: https://codereview.chromium.org/1820073002
26 files changed