Add other OSS-Fuzz fuzzers

[reytchison]

The fuzzer-bot only uses libfuzzer and jazzer. However, there are other standard OSS-Fuzz fuzzers: https://google.github.io/oss-fuzz/getting-started/new-project-guide/#fuzzing_engines. OSS-Fuzz recommends running all of them, Additionally libfuzzer has drawbacks, including it stops on finding the first crash and the default max input size is small (4096 bytes).