Change CASE_NAME to BATCH_NAME

[StephanDeHoop]

Issue
Resolves #9592

Approach
CASE_NAME is a bit of a weird name, BATCH_NAME makes more sense.

(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 -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

[StephanDeHoop]

There is one other place where we use CASE_NAME: test-data/ert/batch_sim/batch_sim.ert RUNPATH <STORAGE>/runpath/<CASE_NAME>/realization-<IENS>/iter-<ITER> , should we change it here to or is this an ERT thing?

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 91.86%. Comparing base (2b41fe2) to head (146b432).
Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #9593   +/-   ##
=======================================
  Coverage   91.85%   91.86%           
=======================================
  Files         433      433           
  Lines       26775    26775           
=======================================
+ Hits        24594    24596    +2     
+ Misses       2181     2179    -2     

Flag	Coverage Δ
cli-tests	39.75% <0.00%> (ø)
everest-models-test	34.58% <100.00%> (+<0.01%)	⬆️
gui-tests	72.15% <0.00%> (+0.02%)	⬆️
integration-test	37.22% <100.00%> (+0.02%)	⬆️
performance-tests	51.95% <0.00%> (-0.03%)	⬇️
test	40.46% <100.00%> (+<0.01%)	⬆️
unit-tests	74.19% <0.00%> (+0.01%)	⬆️

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[codspeed-hq]

CodSpeed Performance Report

Merging #9593 will not alter performance

_{Comparing StephanDeHoop:change_case_name_to_batch_name (146b432) with main (2b41fe2)}

Summary

✅ 22 untouched benchmarks

[yngve-sk]

Looking good