DEBUG-3568 remove agent settings defaulting hack

[p-datadog]

What does this PR do?

Removes the agent settings defaulting hack from the codebase. Agent settings should be passed down from component construction into transports in order to respect user configuration.

Motivation:
Continued DRY refactoring of transport code to support dynamic instrumentation

Change log entry
None

Additional Notes:
I think this PR does not affect customers but not entirely sure.

I would like to remove transport_options in a subsequent PR.

How to test the change?
Existing unit tests

[github-actions]

Thank you for updating Change log entry section 👏

^{Visited at: 2025-03-03 15:46:10 UTC}

[pr-commenter]

Benchmarks

Benchmark execution time: 2025-03-01 06:03:06

Comparing candidate commit c12ab3e in PR branch transport-dry-2 with baseline commit 987b7a6 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: transport-dry-2
Commit report: c12ab3e
Test service: dd-trace-rb

✅ 0 Failed, 20622 Passed, 1370 Skipped, 3m 11.63s Total Time

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 95.45455% with 3 lines in your changes missing coverage. Please review.

Project coverage is 97.69%. Comparing base (987b7a6) to head (c12ab3e).

Files with missing lines	Patch %	Lines
spec/datadog/tracing/transport/http_spec.rb	83.33%	2 Missing ⚠️
lib/datadog/tracing/workers/trace_writer.rb	66.66%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #4440      +/-   ##
==========================================
- Coverage   97.70%   97.69%   -0.01%     
==========================================
  Files        1374     1374              
  Lines       83807    83815       +8     
  Branches     4249     4251       +2     
==========================================
+ Hits        81882    81886       +4     
- Misses       1925     1929       +4     

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[marcotc]

No way! This is an awesome clean up that always looked so ugly! 🙏