[reporting][perf] report InferPrint time taken
[reporting][perf] report InferPrint time taken

Summary:
- InferPrint reports time stats only, logged in `reporting_stats/` as well as a `PerformanceStats` event with `stats_type: reporting`
- Perf reporting can now be registered at one point (with desired start real and cpu times) and triggered later

Reviewed By: dulmarod

Differential Revision: D7332435

fbshipit-source-id: 2e17c7f

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