ccpr: Add an MSAA atlas mode

Adds the option to use a multisampled (or mixed sampled) atlas, and
uses the sample mask and stencil buffer instead of coverage counts.

Bug: skia:
Change-Id: I9fb76d17895ae25208124f6c27e37977ac31b5eb
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/227428
Commit-Queue: Chris Dalton <csmartdalton@google.com>
Reviewed-by: Brian Salomon <bsalomon@google.com>
49 files changed