Summary

This PR improves the determinism oftests/extmod/time_res.py which has been failing intermittently on Windows CI.

Problem: The test was counting unique values returned by time functions over a 2.5-second window, expecting at least 3 unique values for second-resolution functions (gmtime(),localtime()). This approach had fundamental issues:

1. Clock source mismatch: Usedticks_ms() (system tick timer) to measure test duration while samplinggmtime()/localtime() (RTC). On embedded platforms these are different hardware clocks that can drift relative to each other.

2. Race conditions: To see 3 unique second values in a 2.5-second window, the RTC must advance by >2.0 seconds. Due to timing overhead and clock drift, the test could observe only 2.4 seconds of RTC time, causing spurious failures.

3. Windows-specific issues: Windows system clock has ~15ms granularity, making the sample-counting approach particularly unreliable.

Recent CI failures:

• https://github.com/micropython/micropython/actions/runs/18826145552/job/53709126186
• https://github.com/micropython/micropython/actions/runs/18861478955/job/53820524197

Attempted Solution: Replace with direct resolution and bounds testing:

• For each time function, measure value before sleep, sleep appropriate duration, measure after
• Verify the function advanced within expected bounds (80%-200% of sleep time)
• Lower bound checks proper resolution, upper bound catches broken implementations
• 2x upper tolerance handles loaded CI systems while catching real problems
• Eliminates clock drift issues by using appropriate sleep duration for each clock source

Testing

The test logic here is hopefully more robust:

• Second-resolution functions (time(),gmtime(),localtime()): Sleep 1200ms and verify value changed within 1-2.4 second range
• Tick functions (ticks_ms,ticks_us,ticks_ns): Sleep 150ms and verify advanced within 80%-200% of expected
• Upper bound checking: 2x tolerance handles loaded CI systems while catching broken implementations
• Platform handling: Gracefully handles platforms whereticks_cpu returns 0

This approach aims to tests the actual contract of each function (proper time resolution within bounds) rather than a proxy metric (sample counts in specified window).

The test should hopefully now pass reliably on all platforms including Windows, Unix, and embedded targets without platform-specific skip lists.