Add support for Graphite unit tests that modify context options.

We now have a GraphiteContextOptionsProc which is functionally
equivalent to GaneshContextOptionsProc, but works with Graphite
unit tests. This will allow certain Graphite unit tests to
force options on. I will use this in a followup CL to force on
WGSL code generation in Dawn for the SkSL unit tests.

Change-Id: Ie20e23f04aad36da5d5582d9f13b2a3467eee447
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/745616
Commit-Queue: Brian Osman <[email protected]>
Auto-Submit: John Stiles <[email protected]>
Reviewed-by: Brian Osman <[email protected]>
7 files changed