Update tests and instrumentation for gpt-5.1.

[umaannamalai]

This PR updates instrumentation and testing for OpenAI v1 to run against gpt-5.1. The mock server responses for OpenAI v1 now reflect the responses given by gpt-5.1 models.

[github-actions]

✅MegaLinter analysis: Success

Descriptor	Linter	Files	Fixed	Errors	Warnings	Elapsed time
✅ ACTION	actionlint	7		0	0	0.87s
✅ MARKDOWN	markdownlint	7	0	0	0	1.28s
✅ PYTHON	ruff	960	0	0	0	0.95s
✅ PYTHON	ruff-format	960	0	0	0	0.35s
✅ YAML	prettier	15	0	0	0	1.38s
✅ YAML	v8r	15		0	0	5.63s
✅ YAML	yamllint	15		0	0	0.65s

See detailed reports in MegaLinter artifacts

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 81.69%. Comparing base (d0598f9) to head (431c441).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1620      +/-   ##
==========================================
+ Coverage   81.67%   81.69%   +0.02%     
==========================================
  Files         209      209              
  Lines       24392    24392              
  Branches     3870     3870              
==========================================
+ Hits        19923    19928       +5     
+ Misses       3159     3154       -5     
  Partials     1310     1310              

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[TimPansino]

Looks like OpenAI v0 tests are failing, but the current changes look good to me. Fix that and I can approve.