Add tests verifying library is -w warning-clean

[p-datadog]

What does this PR do?

Adds a test that no warnings (ruby -v) are emitted when the tracer is loaded (#4548, #4547, #4548)

Motivation:

Customer feedback that they don't want tracer to emit warnings

Change log entry
None (warnings removed by the other PRs, this PR only adds test coverage)

Additional Notes:

How to test the change?
Tests are added in this PR

[datadog-datadog-prod-us1]

Datadog Report

Branch report: warnings-test-coverage
Commit report: 6e73a1a
Test service: dd-trace-rb

✅ 0 Failed, 20785 Passed, 1370 Skipped, 3m 44.19s Total Time

[Strech]

This will be changed in #4433 with this lines https://github.com/DataDog/dd-trace-rb/pull/4433/files#diff-a2d6d6d68e8af1a8701d9cbb5c926cbae65bd3292847196f7d29979db30cf2b6R53-R57

[p-datadog]

I removed the appsec change.

[pr-commenter]

Benchmarks

Benchmark execution time: 2025-04-03 10:05:39

Comparing candidate commit 6e73a1a in PR branch warnings-test-coverage with baseline commit 1e58013 in branch master.

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

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 97.77%. Comparing base (1e58013) to head (6e73a1a).
Report is 8 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #4550      +/-   ##
==========================================
- Coverage   97.77%   97.77%   -0.01%     
==========================================
  Files        1396     1396              
  Lines       85838    85877      +39     
  Branches     4322     4334      +12     
==========================================
+ Hits        83932    83962      +30     
- Misses       1906     1915       +9     

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[y9v]

awesome!

[Strech]

LGTM