Add wallclock TaskBlock profiler support

[kaahos]

What Does This Do

Add support for wall-clock TaskBlock events, including span-context attribution and native event recording for blocking intervals such as Object.wait and synchronized contention.

Motivation

Make blocking time visible as structured datadog.TaskBlock events instead of relying only on sampled wall-clock frames. It allows to reduce signal emissions.

Additional Notes

Foundation for follow-up LockSupport and Thread.sleep TaskBlock instrumentation.

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Jira ticket: [PROJ-IDENT]