Suppress instrumentation of exporter requests in JdkHttpSender

[thswlsqls]

Fixes #8755

Description

• Wrap the request submission in JdkHttpSender.send() with InstrumentationUtil.suppressInstrumentation(...), so the OpenTelemetry Java agent does not record the exporter's own OTLP requests as CLIENT spans.
• Mirrors OkHttpHttpSender.send(), the other HttpSender implementation, which already wraps its call the same way.
• The flag is set on the calling thread's Context; the agent's executor instrumentation carries it to the sending thread. The okhttp sender relies on the same mechanism when it hands the call to the dispatcher.
• Suppression was added for the okhttp sender in Identifying otel http calls #5918; the JDK sender was never covered by the follow-up work.
• The grpc sender (UpstreamGrpcSender) still lacks suppression. Left for a separate PR.

Testing done

• Added JdkHttpSenderTest#send_suppressesInstrumentation: it injects a Context.taskWrapping(...) executor to stand in for the agent's context propagation and asserts shouldSuppressInstrumentation is true on the sending thread. It fails without the production change and passes with it.
• ./gradlew :exporters:sender:jdk:check — 14 tests passed.
• No docs/apidiffs change: the class lives in an internal package, which japicmp excludes.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 91.29%. Comparing base (e2efec5) to head (0a8594d).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff            @@
##               main    #8757   +/-   ##
=========================================
  Coverage     91.29%   91.29%           
- Complexity    10498    10501    +3     
=========================================
  Files          1006     1006           
  Lines         28338    28340    +2     
  Branches       3581     3581           
=========================================
+ Hits          25870    25874    +4     
  Misses         1675     1675           
+ Partials        793      791    -2     

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Waiting on the author · refreshed 2026-09-02 14:35 UTC

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