Investigate moving off of direct google::protobuf types

When running fix_format script, it complains:
```
Please note: `tools/code_format/check_format.py` no longer checks API `.proto` files, please use `tools/proto_format/proto_format.sh` if you are making changes to the API files
ERROR: From ./../nbperry-nighthawk/source/adaptive_load/metrics_evaluator_impl.cc
ERROR: ./../nbperry-nighthawk/source/adaptive_load/metrics_evaluator_impl.cc:27: unexpected direct dependency on google.protobuf, use the definitions in common/protobuf/protobuf.h instead.
ERROR: ./../nbperry-nighthawk/source/adaptive_load/metrics_evaluator_impl.cc:28: unexpected direct dependency on google.protobuf, use the definitions in common/protobuf/protobuf.h instead.
ERROR: From ./../nbperry-nighthawk/include/nighthawk/adaptive_load/metrics_plugin.h
ERROR: ./../nbperry-nighthawk/include/nighthawk/adaptive_load/metrics_plugin.h:23: unexpected direct dependency on google.protobuf, use the definitions in common/protobuf/protobuf.h instead.
ERROR: ./../nbperry-nighthawk/include/nighthawk/adaptive_load/metrics_plugin.h:26: unexpected direct dependency on google.protobuf, use the definitions in common/protobuf/protobuf.h instead.
ERROR: check format failed. diff has been applied'
```

For now, we are excluding all of Nighthawk from this check. Can we fix this without making a backwards incompatible change?