The fuzzer noticed insufficient guards in IndexExpression::Convert when
converting an array size from an IntLiteral to a SKSL_INT. We had code
in IRGenerator which did this properly, so I moved our array-size
conversion logic into SkSLType and had IndexExpression share it.
Also, a variety of tests around similar error conditions were added.
Change-Id: I51529dea25f9029f81ae236511610069d66be29f
Bug: oss-fuzz:37462
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/441236
Commit-Queue: John Stiles <johnstiles@google.com>
Auto-Submit: John Stiles <johnstiles@google.com>
Reviewed-by: Brian Osman <brianosman@google.com>
