common/util: refactor sleep_for for high-precision sleep

[deanlee]

Changes:

1. Refactored util::sleep_for to use clock_nanosleep (or nanosleep on macOS) for more accurate sleep durations than std::thread::sleep_for, especially for very short sleep durations.
2. support double values for fractional millisecond timing.

This refactor enhances sleep precision across C++ modules, with significant benefits for the RateKeeper class: It also improves event scheduling accuracy in Python modules that rely on stable rate keeping provided by the RateKeeper in the C++ module.

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