feat: emit TaskBlock events for native socket I/O

[kaahos]

What does this PR do?:

Adds native socket I/O TaskBlock instrumentation on Linux by interposing blocking socket APIs, classifying socket file descriptors, and recording synchronous TaskBlock events for owned native I/O waits.

Motivation:

Blocking native I/O is a major source of wall-clock time. Recording these intervals directly avoids intentionally signaling threads while they are blocked in recognized socket operations.

Additional Notes:

This PR includes Linux native interposition, socket/Fd classification, lifecycle handling for unloadable libraries, integration tests, and a native socket I/O benchmark.

How to test the change?:

Automated coverage includes native unit tests for interposition, socket sampling, native block handling, thread-filter suppression, and Java integration tests for native socket TaskBlock behavior.

• ./.claude/commands/build-and-summarize testDebug

Native socket integration tests are Linux-specific and skip on macOS.

For Datadog employees:

• If this PR touches code that signs or publishes builds or packages, or handles credentials of any kind, I've requested a security review (run the dd:platform-security-review skill, or file a request via the PSEC review form).
  bewaire also runs automatically on every PR.
• This PR doesn't touch any of that.
• JIRA: [JIRA-XXXX]

[dd-octo-sts]

CI Test Results

Run: #29573019248 | Commit: 47a49dd | Duration: 16m 20s (longest job)

✅ All 32 test jobs passed

Status Overview

JDK	glibc-aarch64/debug	glibc-amd64/debug	musl-aarch64/debug	musl-amd64/debug
8	-	✅	-	-
8-ibm	-	✅	-	-
8-j9	✅	✅	-	-
8-librca	-	-	✅	✅
8-orcl	-	✅	-	-
11	-	✅	-	-
11-j9	✅	✅	-	-
11-librca	-	-	✅	✅
17	✅	✅	-	-
17-graal	✅	✅	-	-
17-j9	✅	✅	-	-
17-librca	-	-	✅	✅
21	✅	✅	-	-
21-graal	✅	✅	-	-
21-librca	-	-	✅	✅
25	✅	✅	-	-
25-graal	✅	✅	-	-
25-librca	-	-	✅	✅

Legend: ✅ passed | ❌ failed | ⚪ skipped | 🚫 cancelled

Summary: Total: 32 | Passed: 32 | Failed: 0

---

Updated: 2026-07-17 10:37:48 UTC

[dd-octo-sts]

Benchmark Results (commit 4077c10)

Pipeline: https://gitlab.ddbuild.io/DataDog/apm-reliability/benchmarking-platform/-/pipelines/125241502 Commit: 4077c10d812d39470e41a46ffb6dd02dfe10ae05

⚠️ Significant outliers

• 🟢 future-genetic (JDK 25): runtime -3.2% (2072→2005 ms)

Runtime details (per benchmark × JDK)

Benchmark	JDK	Latest	Dev	Δ (dev vs latest)	Issues L/D
akka-uct	21	✅ 10318 ms (21 iters)	✅ 10297 ms (21 iters)	≈ -0.2% (±11.5%)	— / —
akka-uct	25	✅ 8877 ms (24 iters)	✅ 8872 ms (24 iters)	≈ -0.1% (±10%)	— / —
finagle-chirper	21	✅ 5924 ms (33 iters)	✅ 6023 ms (33 iters)	≈ +1.7% (±25.7%)	⚠️ W:3 / ⚠️ W:3
finagle-chirper	25	✅ 5440 ms (36 iters)	✅ 5447 ms (36 iters)	≈ +0.1% (±24%)	⚠️ W:3 / ⚠️ W:3
fj-kmeans	25	✅ 2819 ms (66 iters)	✅ 2768 ms (68 iters)	≈ -1.8% (±2.7%)	— / —
future-genetic	21	✅ 2100 ms (89 iters)	✅ 2118 ms (87 iters)	≈ +0.9% (±2.8%)	— / —
future-genetic	25	✅ 2072 ms (89 iters)	✅ 2005 ms (93 iters)	🟢 -3.2%	— / —
naive-bayes	25	✅ 990 ms (172 iters)	✅ 1017 ms (169 iters)	≈ +2.7% (±31.9%)	— / —
reactors	21	✅ 16610 ms (15 iters)	✅ 16761 ms (15 iters)	≈ +0.9% (±8%)	— / —
reactors	25	✅ 18536 ms (15 iters)	✅ 18473 ms (15 iters)	≈ -0.3% (±2.8%)	— / —

Internal counter details (ddprof)

ddprof internal counters, latest / dev (✅ = 0, · = unavailable):

Benchmark	JDK	Dropped rec	Dropped jvmti	Dropped trace	Skipped WC	AGCT fail	Unwind fail
akka-uct	21	✅ / ✅	✅ / ✅	✅ / 1	2000 / 2002	✅ / ✅	✅ / ✅
akka-uct	25	✅ / ✅	✅ / ✅	1 / 4	2240 / 2285	✅ / ✅	✅ / ✅
finagle-chirper	21	✅ / ✅	✅ / ✅	3 / 4	8783 / 8895	✅ / ✅	✅ / ✅
finagle-chirper	25	✅ / ✅	✅ / ✅	2 / 3	8381 / 7985	✅ / ✅	✅ / ✅
fj-kmeans	21	✅ / ✅	✅ / ✅	4 / ✅	1321 / ✅	✅ / ✅	✅ / ✅
fj-kmeans	25	✅ / ✅	✅ / ✅	2 / 3	1268 / 1276	✅ / ✅	✅ / ✅
future-genetic	21	✅ / ✅	✅ / ✅	✅ / 2	2969 / 2966	✅ / ✅	✅ / ✅
future-genetic	25	✅ / ✅	✅ / ✅	3 / 1	2828 / 2888	✅ / ✅	✅ / ✅
naive-bayes	21	✅ / ✅	✅ / ✅	✅ / ✅	✅ / ✅	✅ / ✅	✅ / ✅
naive-bayes	25	✅ / ✅	✅ / ✅	1 / 4	3471 / 3500	✅ / ✅	✅ / ✅
reactors	21	✅ / ✅	✅ / ✅	✅ / 1	1675 / 1607	✅ / ✅	✅ / ✅
reactors	25	✅ / ✅	✅ / ✅	1 / ✅	1935 / 1843	✅ / ✅	✅ / ✅