refactor(sampling): replace in-tree sampling with libdd-sampling

[Aaalibaba42]

What

Replace dd-trace-rs' local sampling implementation with the shared libdd-sampling crate from libdatadog (introduced in #1927).

Why

The sampling logic was hoisted into libdatadog so it can be reused across tracers. Keeping a
duplicate copy in dd-trace-rs means divergence risk and double maintenance burden.

How

• Deleted files that duplicated logic now in libdd-sampling
• Replaced core::sampling module with direct imports from libdd_sampling.
• Replaced core::constants with a re-export of libdd_sampling::dd_constants.
• Re-exported SamplingRuleConfig from libdd_sampling in the configuration module.
• Adapted otel_mappings.rs to the new trait API:
  • ValueLike method renames (extract_float -> as_float, extract_string -> as_str).
  • SpanProperties::Attribute is now a GAT (type Attribute<'a>).
  • Introduced #[repr(transparent)] newtype wrappers (OtelKeyValue, OtelValue,
    OtelTraceId) to satisfy orphan rules when implementing libdd-sampling traits for
    OpenTelemetry types.
• Removed the lru direct dependency (now transitive via libdd-sampling).
• Updated all import sites across propagation, sampler, span processor, and benchmarks.

Additional Notes

[datadog-datadog-prod-us1]

 

✨ Fix all issues with BitsAI

⚠️ Warnings

🚦 5 Pipeline jobs failed

Test (AWS integrations) | build x86_64-unknown-linux-gnu (AL2023)     

🔧 Fix in code (Fix with Cursor).

Failed to update the lock file Cargo.lock due to the --locked flag.

Test (AWS integrations) | test aarch64-unknown-linux-gnu (AL2023)     

🔧 Fix in code (Fix with Cursor).

Cannot update the lock file Cargo.lock because --locked was passed to prevent this. Consider using --offline instead.

Test (AWS integrations) | test x86_64-unknown-linux-gnu (AL2023)     

🔧 Fix in code (Fix with Cursor).

Cannot update the lock file Cargo.lock because --locked was passed to prevent this. Consider using --offline instead.

View all 5 failed jobs.

ℹ️ Info

No other issues found (see more)

🧪 All tests passed
❄️ No new flaky tests detected

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[paullegranddc]

Closing this as it is a duplicata of #154