fix(litestar): Gate request body collection on data_collection experiment

[ericapisani]

Only attach request body data to events when "incoming_request" is present in the data_collection.http_bodies experiment option (or when the experiment is unset, preserving default behavior).

Refs PY-2419
Refs #6283

[linear-code]

PY-2419

[github-actions]

Codecov Results 📊

✅ 118070 passed | ⏭️ 6732 skipped | Total: 124802 | Pass Rate: 94.61% | Execution Time: 412m 32s

📊 Comparison with Base Branch

Metric	Change
Total Tests	📈 +401
Passed Tests	📈 +403
Failed Tests	📉 -2
Skipped Tests	—

➖ Removed Tests (2)

View removed tests

• test_continuous_profiler_auto_start_and_stop_sampled[non-experiment-gevent]
  • File: tests.profiler.test_continuous_profiler
• test_continuous_profiler_auto_start_and_stop_sampled_span_streaming[experiment-gevent]
  • File: tests.profiler.test_continuous_profiler

All tests are passing successfully.

✅ Patch coverage is 100.00%. Project has 2490 uncovered lines.
✅ Project coverage is 90.22%. Comparing base (base) to head (head).

Coverage diff

@@            Coverage Diff             @@
##          main       #PR       +/-##
==========================================
+ Coverage    90.22%    90.22%        —%
==========================================
  Files          193       193         —
  Lines        25435     25466       +31
  Branches      9346      9372       +26
==========================================
+ Hits         22947     22976       +29
- Misses        2488      2490        +2
- Partials      1434      1434         —

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