Rearrange SkSL pre-include modules to hide things

This makes numerous internal and GLSL types or intrinsics hidden from
public (runtime effect) SkSL. In particular:

- Only core numeric types are visible to all program types. GLSL types
  involving images, textures, and sampling are restricted to internal use.
- sk_Caps is no longer visible to runtime effects.
- The set of intrinsics available to runtime effects is now a separate,
  curated list in sksl_public.sksl. It exactly matches the GLSL ES 1.00
  spec order.
- The blend intrinsics are no longer visible, which also fixes a bug.
  These are nice, but we're not going to offer them yet - they involve
  enums, which creates complications.

Bug: skia:10680
Bug: skia:10709
Bug: skia:10913

Change-Id: I8fa1c94f6e4899f38530bb9cff33d147f6983ab3
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/332597
Commit-Queue: Brian Osman <brianosman@google.com>
Reviewed-by: John Stiles <johnstiles@google.com>
10 files changed