[fuzzing] Add two fuzzers for SkDescriptor

One is an API fuzzer, the other is for deserializing.

Bug: skia:9548
Change-Id: I5923b8fb76f36ec09fca74d5ba82245a8ddb5938
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/249776
Reviewed-by: Herb Derby <herb@google.com>
Commit-Queue: Kevin Lubick <kjlubick@google.com>
7 files changed