Improve dudect test with cropped time analysis

This commit introduces several improvements to the dudect test,
including cropped time analysis and performance optimizations.

- Remove outliers caused by context switches, interrupts, or system
  activity using a percentile-based threshold.

- Store measurements in multiple t-test contexts to track t-tests in
  different percentile thresholds.

- Fix integer overflow and improve the efficiency in the 'cmp()'
  function by using a branch-free comparison '(a > b) - (a < b)'.

- Optimize the calculation of 'max_t' and 'max_tau' by deferring
  computations until necessary, reducing unnecessary calculation when
  measurements are insufficient.

Change-Id: I5e1571f31ac1e3082ae274d79248889c94d8b512

Author: BennyWang1007