Improve Test Robustness and Reliability

[arturobernalg]

This PR addresses intermittent test failures observed in the AIMDBackoffManager test suite.

Test methods backoffDoesNotAdjustDuringCoolDownPeriod, probeDoesNotAdjustDuringCooldownPeriod , probeDoesNotAdjustDuringCooldownPeriod and backoffDoesNotAdjustDuringCoolDownPeriod previously used Thread.sleep() to mimic passage of time. However, this approach proved to be unstable and led to random test failures, largely due to the non-guarantee of precise timing with Thread.sleep().

To mitigate this, we adopted a busy waiting approach using System.currentTimeMillis(). In essence, we loop until a specific future time (1 millisecond ahead) is reached. Although this is generally not an ideal solution for production code due to its CPU-intensive nature, it is a reasonable compromise in this specific testing scenario. The busy waiting period is extremely short (1 millisecond), and this approach significantly improves test stability without introducing significant overhead.

The changes in this PR should not affect the functionality of the AIMDBackoffManager, but instead ensure our tests are reliable and consistent.