Extend hook's teardown metadata with warmup/calibration flags

[sergey-miryanov]

I'm working on gc-monitor and have implemented a pyperf hook. The hook's teardown function writes collected run data to an intermediate file, but there's currently no way to distinguish between warmup, calibration, and measurement runs.

Would it make sense to extend the metadata dictionary passed to teardown with additional context, such as {"is_warmup": is_warmup, "calibrate_loops": calibrate_loops}?