feat(propagation): baggage support and automatic propagation

[ZStriker19]

What does this PR do?
Following the spec here: https://www.w3.org/TR/baggage/ we implement baggage for the Ruby tracer. The otel drop in support will be added in a future PR.
Motivation:

Change log entry

• Tracing: Added support for W3C Baggage extraction and injection by default.
• Tracing: Adds api method to access and modify baggage object.

Additional Notes:

How to test the change?
Tests were added in the repo and it passes the weblog system-tests. It will not pass the parametric system-tests because of the difficulty of managing the context in server.rb, not due an issue of implementation of the actual feature.

[ZStriker19]

Following up from #4371 which was merged with issues

[pr-commenter]

Benchmarks

Benchmark execution time: 2025-03-19 14:15:03

Comparing candidate commit e827430 in PR branch zachg/baggage_support with baseline commit 5544d29 in branch master.

Found 0 performance improvements and 0 performance regressions! Performance is the same for 31 metrics, 2 unstable metrics.

[datadog-datadog-prod-us1]

Datadog Report

Branch report: zachg/baggage_support
Commit report: e827430
Test service: dd-trace-rb

✅ 0 Failed, 20723 Passed, 1371 Skipped, 3m 19.55s Total Time

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 99.24242% with 2 lines in your changes missing coverage. Please review.

Project coverage is 97.69%. Comparing base (4306938) to head (e827430).
Report is 4 commits behind head on master.

Files with missing lines	Patch %	Lines
lib/datadog/tracing/distributed/baggage.rb	97.10%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #4505      +/-   ##
==========================================
- Coverage   97.70%   97.69%   -0.01%     
==========================================
  Files        1381     1383       +2     
  Lines       84017    84260     +243     
  Branches     4253     4278      +25     
==========================================
+ Hits        82085    82321     +236     
- Misses       1932     1939       +7     

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