Simplify VarDeclaration by removing multi-dimensional array support.

Maintaining an array of Expression-based sizes is not necessary as GLSL
only supports a single dimension, and doesn't allow any expression other
than a constant integer or nothing (meaning "unsized").

Change-Id: I01b5f88b94234a27e694aa2fc087f9d5f01b99c5
Bug: skia:11026
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/340341
Commit-Queue: John Stiles <johnstiles@google.com>
Reviewed-by: Ethan Nicholas <ethannicholas@google.com>
Auto-Submit: John Stiles <johnstiles@google.com>
10 files changed