Change obs_and_responses test to benchmark

[eivindjahren]

Fixes unreliable hard limit to benchmark we can control over time

• PR title captures the intent of the changes, and is fitting for release notes.
• Added appropriate release note label
• Commit history is consistent and clean, in line with the contribution guidelines.
• Make sure unit tests pass locally after every commit (git rebase -i main --exec 'pytest tests/ert/unit_tests -n logical -m "not integration_test"')

When applicable

• When there are user facing changes: Updated documentation
• New behavior or changes to existing untested code: Ensured that unit tests are added (See Ground Rules).
• Large PR: Prepare changes in small commits for more convenient review
• Bug fix: Add regression test for the bug
• Bug fix: Create Backport PR to latest release

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 91.88%. Comparing base (4550d40) to head (4a712cf).
Report is 28 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #9567      +/-   ##
==========================================
+ Coverage   91.85%   91.88%   +0.02%     
==========================================
  Files         433      433              
  Lines       26764    26788      +24     
==========================================
+ Hits        24583    24613      +30     
+ Misses       2181     2175       -6     

Flag	Coverage Δ
cli-tests	39.74% <ø> (-0.03%)	⬇️
everest-models-test	34.58% <ø> (-0.09%)	⬇️
gui-tests	72.12% <ø> (-0.03%)	⬇️
integration-test	37.18% <ø> (-0.03%)	⬇️
performance-tests	51.94% <ø> (-0.06%)	⬇️
test	40.68% <ø> (+0.20%)	⬆️
unit-tests	74.19% <ø> (+0.04%)	⬆️

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[codspeed-hq]

CodSpeed Performance Report

Merging #9567 will not alter performance

_{Comparing eivindjahren:change_obs_and_responses_test_to_benchmark (4a712cf) with main (d9088eb)}

Summary

✅ 22 untouched benchmarks
🆕 2 new benchmarks

Benchmarks breakdown

	Benchmark	main	eivindjahren:change_obs_and_responses_test_to_benchmark	Change
🆕	test_speed_performance_of_doing_es_update[setup_es_benchmark0]	N/A	84.1 ms	N/A
🆕	test_time_performance_of_joining_observations_and_responses[setup_benchmark0]	N/A	12.6 ms	N/A

[larsevj]

🐎