Add anisotropic option to SkSamplingOptions.

Implement on GPU.

Bug: skia:13036
Change-Id: I35d760596c4f8faaec27fccf284b70802fcf3f9b
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/524757
Commit-Queue: Brian Salomon <bsalomon@google.com>
Reviewed-by: Brian Osman <brianosman@google.com>
Reviewed-by: Michael Ludwig <michaelludwig@google.com>
25 files changed