Switch to scenic allocator and Image3 API.
Co-authored-by: NDavid Reveman <reveman@google.com>

https://skia.googlesource.com/skia.git/+log/3c1ed9cbe23d..5c5f09bc28b8

2021-04-14 csmartdalton@google.com Redirect fillRectWithEdgeAA to fillRectToRect when edgeAA==kAll
2021-04-14 csmartdalton@google.com Revert GrOpsRenderPass::fUsesMSAASurface
2021-04-14 mtklein@google.com remove SkNx::rsqrt()
2021-04-14 johnstiles@google.com Fix for loops with multiple init-variables in Metal.
2021-04-14 johnstiles@google.com Add unit test for for-loop with multiple variables.
2021-04-14 bsalomon@google.com No VS specialization for identity or scale/trans in reduced shader mode
2021-04-14 mtklein@google.com remove unused SkNx::invert()
2021-04-14 reed@google.com Demo different sampling options
2021-04-14 reed@google.com Expose drawGlyphs to CK
2021-04-14 adlai@google.com Surface resource cache through cmdline flag
2021-04-14 senorblanco@chromium.org Update Skia-Dawn for recent Dawn API changes.
2021-04-14 bsalomon@google.com Replace GrConstColorProcessor with a runtime FP

If this roll has caused a breakage, revert this CL and stop the roller
using the controls here:
https://autoroll.skia.org/r/skia-flutter-autoroll
Please CC brianosman@google.com on the revert to ensure that a human
is aware of the problem.

To report a problem with the AutoRoller itself, please file a bug:
https://bugs.chromium.org/p/skia/issues/entry?template=Autoroller+Bug

Documentation for the AutoRoller is here:
https://skia.googlesource.com/buildbot/+doc/master/autoroll/README.md