Use monotonic clock to compute durations

[rhcarvalho]

Searching for time.time() in the code base reveals many cases where we use it to compute durations, when it would be more robust to use a monotonic clock.

On Python 3.3+ this would be time.monotonic() or time.perf_counter() (or even time.process_time()), as appropriate.

On Python 2.x and <3.3 there is https://pypi.org/project/monotonic/.

See also https://www.python.org/dev/peps/pep-0418/.

[joshuarli]

Yeah, I've seen @beezz use monotonic clock in some ops code and it's good. This would maybe require a bit of care auditing all the time usage, as I'm not sure if we rely on the assumption on some deltas being >= 0, for example.

[github-actions]

This issue has gone three weeks without activity. In another week, I will close it.

But! If you comment or otherwise update it, I will reset the clock, and if you label it Status: Accepted, I will leave it alone ... forever!

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"A weed is but an unloved flower." ― Ella Wheeler Wilcox 🥀