Support markers (custom matrices) in SkVertices Attributes

Bug: skia:9984
Change-Id: Ie799ffa19304978e2076f9ba790e8a34c1b03adf
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/283225
Reviewed-by: Brian Salomon <bsalomon@google.com>
Commit-Queue: Brian Osman <brianosman@google.com>
13 files changed