Added (color=8888|f16|srgb) option to gpu configurations, along with gpuf16 and gpusrgb predefined configs. Runs the gpu backend in gamma-correct mode (with either FP16 linear or sRGB 8888 frambuffers).

BUG=skia:
GOLD_TRYBOT_URL= https://gold.skia.org/search2?unt=true&query=source_type%3Dgm&master=false&issue=1750383002

Committed: https://skia.googlesource.com/skia/+/a6f58194733c1c50e4fe5f98585e42344f29b6f0

Review URL: https://codereview.chromium.org/1750383002
6 files changed