Move shader caps into SkSL context.

Previously these existed in each Program, but they are unchanging for
the lifetime of the Compiler. Also, their presence in the Context will
allow the SkSL::Setting class to access them outside of the IRGenerator.

Also, removed some code which allowed the IRGenerator to support null
shader-caps; this never actually happens. (The Compiler asserts that
they are non-null; the GLSL code generator uses the caps bits without a
null check, etc.)

Change-Id: Id58743a0c2ac068cb60ec35648b4f758bf28bbe3
Bug: skia:11365, skia:11319
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/375067
Auto-Submit: John Stiles <johnstiles@google.com>
Reviewed-by: Brian Osman <brianosman@google.com>
10 files changed