[graphite] Pass SkUniforms around as an SkSpan

Bug: skia:12701
Change-Id: Iee63650517a739029f81121cabd45dfcc2e8fa38
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/502698
Reviewed-by: Michael Ludwig <michaelludwig@google.com>
Commit-Queue: Robert Phillips <robertphillips@google.com>
5 files changed