Move GrVertexColor to skgpu::VertexColor

Bug: skia:12524
Change-Id: Iac60a99331fefe9e997b61c4b2b329e39b95ae6e
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/470197
Commit-Queue: Chris Dalton <csmartdalton@google.com>
Reviewed-by: Michael Ludwig <michaelludwig@google.com>
Reviewed-by: Greg Daniel <egdaniel@google.com>
13 files changed