add Netty epoll/NIO-select TaskBlock instrumentation

[kaahos]

What Does This Do

Adds TaskBlock instrumentation for NIO Selector.select and Netty epoll event-loop blocking, following the same pattern established for LockSupport (#11545) and Thread.sleep (#11546). Includes:

• nio-select and netty-epoll-4.1 instrumentation modules
• Forked instrumentation tests and disabled/enabled coverage tests
• End-to-end smoke tests (NioSelectTaskBlockProfilingTest, NettyEpollTaskBlockProfilingTest) asserting on resulting TaskBlock recordings
• Native I/O TaskBlock smoke coverage (NativeIoTaskBlockProfilingTest)

This is stacked on #11546 (Thread.sleep), #11545 (LockSupport), and #11544 (foundational TaskBlock support), and should be reviewed/merged in that order.

Motivation

Selector-based I/O waits and Netty's epoll event loop are common sources of off-CPU time that for now show up only as generic sampled wall-clock frames. Emitting structured datadog.TaskBlock events for these operations, as already done for locks and sleeps, gives users accurate attribution of NIO and Netty event-loop blocking without relying solely on stack sampling.

Additional Notes

• CI (.gitlab-ci.yml) updated to build/track the corresponding java-profiler TaskBlock branch changes needed for this coverage.
• Depends on the same java-profiler PR #666 as Add wallclock TaskBlock profiler support #11544.

Contributor Checklist

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Jira ticket: [PROJ-IDENT]