DI permit taking length of hashes in EL

[p-datadog]

What does this PR do?

Adds support for taking lengths of hashes in dynamic instrumentation expression language.

Motivation:
Feature parity / we have a system test checking for this functionality.

Change log entry
Yes: dynamic instrumentation: support length operation on hashes in expression language

Additional Notes:

This PR also adds additional test cases that are tested by system tests to detect failures in the respective code earlier and have test coverage for them in dd-trace-rb (@value usage when iterating hashes, length of arrays).

How to test the change?
Unit tests added

[github-actions]

Thank you for updating Change log entry section 👏

^{Visited at: 2025-11-03 13:05:21 UTC}

[datadog-official]

✅ Tests

🎉 All green!

❄️ No new flaky tests detected
🧪 All tests passed

🎯 Code Coverage
• Patch Coverage: 100.00%
• Total Coverage: 98.55% (+0.02%)

View detailed report

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🔗 Commit SHA: 7979323 | Docs | Datadog PR Page | Was this helpful? Give us feedback!}

[pr-commenter]

Benchmarks

Benchmark execution time: 2025-11-03 15:14:05

Comparing candidate commit 7979323 in PR branch di-hash-length with baseline commit 05283ad in branch master.

Found 0 performance improvements and 0 performance regressions! Performance is the same for 44 metrics, 2 unstable metrics.