Add oss-fuzz compatible fuzzers for sksl2*

Bug: skia:
Change-Id: I468517481fcae42155c4363d817405455181d3c3
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/199721
Reviewed-by: Ethan Nicholas <ethannicholas@google.com>
Commit-Queue: Kevin Lubick <kjlubick@google.com>
5 files changed