Move all runtime effect error tests to runtime_errors

Also renamed Discard to IllegalStatements, and added testing of while
and do loops.

Change-Id: Ibacf69131267a0436808e2e022ad126704af16ef
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/353706
Commit-Queue: Brian Osman <brianosman@google.com>
Commit-Queue: John Stiles <johnstiles@google.com>
Auto-Submit: Brian Osman <brianosman@google.com>
Reviewed-by: John Stiles <johnstiles@google.com>
11 files changed