Refactor and rename summary_block()

[berland]

The logic for determining stable was not correct, if the summary
file was not stable after two reads, it would always timeout. Behaviour
is not defined by tests.

Issue
Part of #8925

Approach
🧠

• 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 91.64%. Comparing base (fc6244f) to head (ac0cf14).
Report is 7 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #8927      +/-   ##
==========================================
- Coverage   91.65%   91.64%   -0.02%     
==========================================
  Files         343      343              
  Lines       21168    21162       -6     
==========================================
- Hits        19402    19394       -8     
- Misses       1766     1768       +2     

Flag	Coverage Δ
cli-tests	39.82% <ø> (-0.01%)	⬇️
gui-tests	73.79% <ø> (-0.04%)	⬇️
performance-tests	50.39% <ø> (-0.02%)	⬇️
unit-tests	80.28% <ø> (-0.03%)	⬇️

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[eivindjahren]

🧹