fix(config visibility): fix system test related to reporting of trace sampler and span sampler

[anna-git]

Description

Previous PR #268 accidentally broke the system test library_settings as we're not filling the telemetry vector with final.metadata anymore but from a separate array and this array wasn't passed by to finalize_config for span and trace sampler.

Motivation

Fix system test Test_Environment::test_library_settings

Additional Notes

Ran parametric tests locally and they all pass. (I thought they did with the previous PR as well but turned out I had a cached docker image)

https://datadoghq.atlassian.net/browse/APMAPI-1784

[pr-commenter]

Benchmarks

Benchmark execution time: 2026-01-21 10:14:53

Comparing candidate commit 9000fef in PR branch anna/config-visibility-fix-sample-reporting with baseline commit ef6d81e in branch main.

Found 0 performance improvements and 0 performance regressions! Performance is the same for 1 metrics, 0 unstable metrics.

[datadog-datadog-prod-us1]

🎯 Code Coverage
• Patch Coverage: 94.12%
• Overall Coverage: 87.77%

View detailed report

_{This comment will be updated automatically if new data arrives.
🔗 Commit SHA: 9000fef | Docs | Datadog PR Page | Was this helpful? Give us feedback!}

[codecov-commenter]

Codecov Report

❌ Patch coverage is 94.11765% with 3 lines in your changes missing coverage. Please review.
✅ Project coverage is 87.76%. Comparing base (7a55843) to head (9000fef).
⚠️ Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
src/datadog/trace_sampler_config.cpp	80.00%	2 Missing ⚠️
src/datadog/datadog_agent_config.cpp	50.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #272      +/-   ##
==========================================
- Coverage   87.83%   87.76%   -0.07%     
==========================================
  Files          84       84              
  Lines        5664     5658       -6     
==========================================
- Hits         4975     4966       -9     
- Misses        689      692       +3     

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[dmehala]

The fix works as intended. That said, it will be cleaner to populate all_sources_configs by merging the configuration sources from the trace and span samplers using the results of finalize_config, leveraging the same mechanism used for metadata. This would help keep the approach consistent and easier to maintain.

[dmehala]

I prefer the current behaviour where the configuration source/data are returned by finalize_config, then merged into the final all_sources_configs. Instead of adding a superfluous argument to finalize_config.

[anna-git]

good point thank you, I got worried about creating a new hash table in these types, but in the end not changing signatures is definitely cleaner, I changed it in bcc8bd6

[anna-git]

Also added a few more asserts in commit 5dec43d