Upgrade pytest-codspeed to 1.2.0

[art049]

This will fix the benchmark results variability seen in #330 and #336.
It will probably create some regression since the core calling logic has been changed but this kind of refactoring affecting the results should be the last since the internal structure is now more modular.

[codspeed-hq]

CodSpeed Performance Report

Merging #337 upgrade-pytest-codspeed-1-2-0 (d31327c) will not alter performances.

Summary

🔥 1 improvements
❌ 2 regressions
✅ 60 untouched benchmarks

🆕 0 new benchmarks
⁉️ 0 dropped benchmarks

Benchmarks breakdown

	Benchmark	main	upgrade-pytest-codspeed-1-2-0	Change
❌	test_core_python_not_fs	328.6 µs	361.8 µs	-10.08%
🔥	test_many_models_core_model	100.4 ms	15 ms	85.10%
❌	test_arguments	43.7 µs	49 µs	-12.02%

[codecov-commenter]

Codecov Report

Merging #337 (d31327c) into main (e146483) will not change coverage.
The diff coverage is n/a.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #337   +/-   ##
=======================================
  Coverage   97.16%   97.16%           
=======================================
  Files          57       57           
  Lines        6952     6952           
  Branches       46       46           
=======================================
  Hits         6755     6755           
  Misses        197      197           

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[samuelcolvin]

Thanks so much.