support 64-bit PixelFormats

RGBA U16/F16 diffs both look pretty much good here.

There are a few F16 diffs to look at, but those are likely one-off diffs
in effect implementation (e.g. SkRasterPipeline clamping somewhere we've
since decided to not clamp in the new SkVM implementation).

Last thing TODO is JIT 64-bit loads and stores to get this all to JIT.

Change-Id: Iadc65c1fc13c32d67d7c7243312d4c90d921dbde
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/303272
Reviewed-by: Herb Derby <herb@google.com>
Commit-Queue: Mike Klein <mtklein@google.com>
2 files changed