Combine snake oils

[frode-aarstad]

Issue
Resolves #12784

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 'just rapid-tests')

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: Add backport label to latest release (format: 'backport release-branch-name')

[ertomatic]

Screenshots differ from baselines. A baseline update PR has been prepared: equinor/ert-testdata#46

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 91.39%. Comparing base (137d9f2) to head (c206ecf).

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #13980      +/-   ##
==========================================
- Coverage   91.40%   91.39%   -0.02%     
==========================================
  Files         481      481              
  Lines       34213    34213              
==========================================
- Hits        31273    31268       -5     
- Misses       2940     2945       +5     

Flag	Coverage Δ
cli-tests	35.96% <ø> (ø)
fuzz	43.58% <ø> (ø)
gui-tests	59.22% <ø> (-0.01%)	⬇️
performance-and-unit-tests	79.45% <ø> (-0.02%)	⬇️
test	46.02% <ø> (ø)

Flags with carried forward coverage won't be shown. Click here to find out more.
see 2 files with indirect coverage changes

[codspeed-hq]

Merging this PR will not alter performance

✅ 36 untouched benchmarks

---

_{Comparing frode-aarstad:combine-snake-oils (c206ecf) with main (137d9f2)}

[xjules]

Out of curiosity, why we need to have a separate OP1 and OP2 groups?

[frode-aarstad]

It the way its done in snake_oil_field.py

[xjules]

I think it is good!
Please provide a commit message explaining (on a higher level) the changes.

[eilskra]

This seems to be what triggered equinor/ert-testdata#46, attempt at more info in:
#14017 (comment)