Fix: Prevent state leakage in AsyncThreadContext tests

[Kcruz28]

AsyncThreadContextDefaultTest was a state leak. Since the test is parameterized, the ThreadContext wasn't being reset between runs. This meant data from a previous test execution could sometimes carry over and cause assertions in the next run to fail.

The fix is to ensure the ThreadContext is cleared before every test execution.

I added a @BeforeEach method to the shared base class, AbstractAsyncThreadContextTestBase.java. This new method simply calls ThreadContext.clearAll(), guaranteeing that each test starts with a clean slate.

This change prevents the state leak and makes the test reliable. Placing the fix in the base class also protects other tests that inherit from it against similar issues.

Fixes: #3049

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