NVFuser userbenchmarks - use JSON output format (#920)
Summary:
Pull Request resolved: https://github.com/pytorch/benchmark/pull/920
Ran `python run_benchmark.py nvfuser --filter autogen-4`.
There's some stdout, plus the following output that was dumped into `.userbenchmark/nvfuser/metrics-20220519221324.json`:
```json
{
"name": "nvfuser",
"environ": {
"pytorch_git_version": "fdd5462cd93af8a835e5e5616d6c85c7553b9be1"
},
"metrics": {
"no_fuser:autogen-4": 0.360220073023811,
"nnc-static:autogen-4": 0.34597328188829124,
"nnc-dynamic:autogen-4": 0.3488327481318265,
"nvfuser:autogen-4": 0.4082540248055011
}
}
```
Test Plan: Imported from OSS
Reviewed By: eellison, xuzhao9
Differential Revision: D36553164
Pulled By: davidberard98
fbshipit-source-id: 5487be82e1466b50a3bd102c5fe54bb000334900
