Switch to vertex colors rather than uniforms for color in Ellipse/Circle/RRect/DRRect

Switch to vertex colors rather than uniforms for color in Ellipse/Circle/RRect/DRRect

[Notes:]
- Performance delta on desktop looked like noise. I'm curious what the results will be on low-end mobile GPUs. I'm still trying to figure out how I determine that with perf, etc...
- There appeared to be a single one-pixel image diff while running dm, if I'm understanding the results of skdiff correctly, so that's probably good news?
- Should I include anyone else on the review?

BUG=skia:
GOLD_TRYBOT_URL= https://gold.skia.org/search2?unt=true&query=source_type%3Dgm&master=false&issue=1675833002

Review URL: https://codereview.chromium.org/1675833002