Reland "Run unit tests to verify SkSL folding behavior."

This is a reland of 4ecab92584557c1a08e6edced5b0fdd2496eb2f0

This reland folds in subsequent code cleanups and disables a test that
failed on Android + Vulkan.

Original change's description:
> Run unit tests to verify SkSL folding behavior.
>
> The unit test loads SkSL source files from `resources/sksl`, compiles
> the code, and uses SkRuntimeEffect to render a pixel using the effect.
> If solid green is rendered, the test passes.
>
> Change-Id: I2ccb427a907975ae84aee19d8e68d774b2cb638c
> Bug: skia:11009
> Reviewed-on: https://skia-review.googlesource.com/c/skia/+/355983
> Commit-Queue: John Stiles <johnstiles@google.com>
> Auto-Submit: John Stiles <johnstiles@google.com>
> Reviewed-by: Brian Osman <brianosman@google.com>

Bug: skia:11009
Change-Id: I09196c8ca3041e8957324a0cbb7f7d6963c6e4e7
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/358523
Auto-Submit: John Stiles <johnstiles@google.com>
Commit-Queue: Ethan Nicholas <ethannicholas@google.com>
Reviewed-by: Ethan Nicholas <ethannicholas@google.com>
5 files changed