[graphite] Use CombinationBuilder to create SkPaintParamsKeys directly

Bug: skia:12701
Change-Id: I53bbabb2aba44e3bfc215df81dae1ae59d149263
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/544319
Reviewed-by: Michael Ludwig <michaelludwig@google.com>
Reviewed-by: Greg Daniel <egdaniel@google.com>
Commit-Queue: Robert Phillips <robertphillips@google.com>
7 files changed