Add --output-iter-metrics flag to cpu userbenchmark scripts (#2600)
Summary:
Adds a new `--output-iter-metrics` flag which adds per-iteration metrics to benchmark result JSON files. This allows us to do our own statistical analysis and comparison of latency/throughput.
Pull Request resolved: https://github.com/pytorch/benchmark/pull/2600
Reviewed By: xuzhao9
Differential Revision: D71902373
Pulled By: FindHao
fbshipit-source-id: 8216ff91f03e220ff6b7631c038d369206736935