lcd blits for sRGB

Unimplemented for F16 for the moment, but not needed yet.
Surprisingly not much slower than current impl (not srgb correct)

GOLD_TRYBOT_URL= https://gold.skia.org/search2?unt=true&query=source_type%3Dgm&master=false&issue=1707883002

Review URL: https://codereview.chromium.org/1707883002
3 files changed