Guard Garbage Collection Metrics Against Re-Entrant Calls

[TimPansino]

Overview

• Add flag to prevent re-entrant calls to _GCDataSource.record_gc() to prevent infinite recursion on Python 3.13+.
• Improve caching of IS_PYPY in gc_data.py for performance.
• Add regression test that bypasses garbage collection infrastructure and directly unit tests re-entrant calls to _GCDataSource.record_gc().
  • If we can find a reliable way to trigger the original issue in testing, we could add a better regression test here as well.

Related Github Issue

Closes #1706

Testing

1. Revert the changes made to gc_data.py.
2. Run the agent_unittests suite. Observe the tests hanging forever when simulating re-entrant invocations of record_gc.
3. Restore the changes to gc_data.py.
4. Run the agent_unittests suite. Observe the tests passing due to the new guard in place preventing re-entrant calls.

[github-actions]

✅MegaLinter analysis: Success

Descriptor	Linter	Files	Fixed	Errors	Warnings	Elapsed time
✅ ACTION	actionlint	8		0	0	1.18s
✅ MARKDOWN	markdownlint	7	0	0	0	1.27s
✅ PYTHON	ruff	1030	0	0	0	1.36s
✅ PYTHON	ruff-format	1030	0	0	0	0.42s
✅ YAML	prettier	19	0	0	0	1.5s
✅ YAML	v8r	19		0	0	5.88s
✅ YAML	yamllint	19		0	0	0.77s

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[codecov-commenter]

Codecov Report

❌ Patch coverage is 86.36364% with 3 lines in your changes missing coverage. Please review.
✅ Project coverage is 81.91%. Comparing base (77df266) to head (d63e8fe).

Files with missing lines	Patch %	Lines
newrelic/samplers/gc_data.py	86.36%	1 Missing and 2 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1707      +/-   ##
==========================================
- Coverage   81.97%   81.91%   -0.06%     
==========================================
  Files         214      214              
  Lines       25803    25810       +7     
  Branches     4082     4083       +1     
==========================================
- Hits        21151    21142       -9     
- Misses       3261     3272      +11     
- Partials     1391     1396       +5     

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