fix: stabilize flaky ParamFlowDefaultCheckerTest by using mocked time

[EvanYao826]

Summary

The test testParamFlowDefaultCheckSingleValueCheckQpsMultipleThreads was flaky because it used real time (TimeUnit.sleep and wall-clock-based loops) for concurrent assertions. This caused race conditions when the test ran in isolation vs. after other tests.

Root Cause

The test's second phase used TimeUtil.currentTimeMillis() in a busy loop with real thread sleep, making the assertion result depend on:

• Exact thread scheduling timing
• Whether a previous test's time mock was still active
• Wall-clock drift during the 2.5-second loop

Fix

• Wrapped the entire test in MockedStatic<TimeUtil> (consistent with all other tests in this class)
• Replaced the real-time busy loop with a clean second round of concurrent requests after advancing the mock clock past the duration window
• This makes the test deterministic regardless of thread scheduling or test execution order

Fixes #2426

[oss-sentinel-ai]

Summary

The PR replaces the wall-clock delay with mocked time, but the thread-local static mock does not affect the concurrent checks, so the revised test is not correct or deterministic.

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Automated review by github-manager-bot

[oss-sentinel-ai]

MockedStatic scopes stubbing to the thread that created it, so the 40 worker threads still call the real TimeUtil.currentTimeMillis() inside ParamFlowChecker. Advancing this mock therefore does not advance their token-counter timestamps; the second round runs less than three real seconds after the first and is rejected rather than allowing threshold requests. Use a time source that is shared by the worker threads (or install the static mock within each worker) before removing the real wait.