Disallow multi-dimensional arrays in SkSL.

GLSL only allows one-dimensional arrays. This CL lowers SkSL's array
dimensionality limit from eight to one, and fixes all the tests that
this breaks. The rest of the code still technically supports
arbitrarily-deep array dimensionality; there are many opportunities for
code cleanup and simplification in followup CLs.

Change-Id: I0fc31e4626649ec69d40c5f5597b3924de298df0
Bug: skia:11026
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/340339
Commit-Queue: John Stiles <johnstiles@google.com>
Reviewed-by: Ethan Nicholas <ethannicholas@google.com>
Auto-Submit: John Stiles <johnstiles@google.com>
21 files changed