Backport Ert 12.1: Ensure cpu_seconds is always reported increasingly

[berland]

The summation of cpu_seconds for a process and all its descendants can never work properly during teardown of a process tree, as the root process typically outlives its children. Thus, the maximum observed cpu_seconds for a process tree is always the best estimate of the correct sum.

Issue
Resolves #my_issue

Approach
Short description of the approach

(Screenshot of new behavior in GUI if applicable)

• 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 tests/everest -n auto --hypothesis-profile=fast -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 91.86%. Comparing base (416a1db) to head (3c1acf8).

Additional details and impacted files

@@               Coverage Diff                @@
##           version-12.1    #9873      +/-   ##
================================================
- Coverage         91.86%   91.86%   -0.01%     
================================================
  Files               433      433              
  Lines             26826    26828       +2     
================================================
  Hits              24645    24645              
- Misses             2181     2183       +2     

Flag	Coverage Δ
cli-tests	39.69% <0.00%> (-0.01%)	⬇️
everest-models-test	34.56% <100.00%> (-0.02%)	⬇️
gui-tests	72.10% <100.00%> (+<0.01%)	⬆️
integration-test	38.66% <100.00%> (-0.01%)	⬇️
performance-tests	51.89% <100.00%> (-0.01%)	⬇️
test	40.03% <100.00%> (-0.02%)	⬇️
unit-tests	74.10% <100.00%> (-0.01%)	⬇️

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[codspeed-hq]

CodSpeed Performance Report

Merging #9873 will degrade performances by 82.62%

_{Comparing berland:version-12.1-cpusecondbackport (3c1acf8) with main (1f0380c)}

Summary

⚡ 5 improvements
❌ 1 regressions
✅ 18 untouched benchmarks

⚠️ Please fix the performance issues or acknowledge them on CodSpeed.

Benchmarks breakdown

	Benchmark	BASE	HEAD	Change
❌	test_and_benchmark_adaptive_localization_with_fields	3 s	17 s	-82.62%
⚡	test_direct_dark_performance[gen_x: 20, sum_x: 20 reals: 10-gen_data-get_parameters]	252.8 µs	146 µs	+73.15%
⚡	test_direct_dark_performance[gen_x: 20, sum_x: 20 reals: 10-gen_data_with_obs-get_parameters]	251.9 µs	144.7 µs	+74.05%
⚡	test_direct_dark_performance[gen_x: 20, sum_x: 20 reals: 10-summary-get_parameters]	259.2 µs	149 µs	+73.93%
⚡	test_direct_dark_performance[gen_x: 20, sum_x: 20 reals: 10-summary_with_obs-get_parameters]	252.7 µs	144.2 µs	+75.21%
⚡	test_direct_dark_performance_with_storage[gen_x: 20, sum_x: 20 reals: 10-gen_data-get_record_observations]	1.6 ms	1.3 ms	+16.68%