Example Fuzzers

Please note: some of the specific behaviors of these fuzzers are currently relied upon for manual end-to-end and integration testing, so when making any changes please ensure that fx fuzz e2etest still passes and update it if necessary. For cpp:crash_fuzzer and cpp:overflow_fuzzer in particular, behavioral changes should additionally be validated against the ClusterFuzz integration tests. See fxbug.dev/61973 for more details.