Parse new Fuchsia fuzzer GN metadata. (#2048)
Parse new Fuchsia fuzzer GN metadata. (#2048)

The Fuchsia GN templates for fuzzers changed the metadata emitted to
fuzzers.json:
https://fuchsia-review.googlesource.com/c/fuchsia/+/425274

This change allows ClusterFuzz to recognize and parse either the newer
or older style of metadata.

Tested with existing integration tests on newer Fuchsia builds.
google/clusterfuzz,google/clusterfuzz,google/clusterfuzz,google/clusterfuzz,google/clusterfuzz,google/clusterfuzz,google/clusterfuzz,google/clusterfuzz