Make it safe to include SkRuntimeEffect.h from client code

Bundling the pipeline stage arguments also simplifies the code in
several spots.

Change-Id: I85e81b436a39378f753cc9404b6eeb27fe055525
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/261778
Reviewed-by: Brian Salomon <bsalomon@google.com>
Commit-Queue: Brian Osman <brianosman@google.com>
8 files changed