Add dev documentation on everest vs ert data models

[StephanDeHoop]

Issue
Resolves #9619

Approach
Attempts to clarify the differences between ERT and EVEREST data models. There are things in here that need revision (like the mapping, these equations work but not sure if it makes sense in all cases of optimization meaning gradient vs. derrivative free methods etc.). Also, with Yngve we suggest a couple of name changes:

• simulation -> ert_realization (at least in the code, since they are synonymous)
• geo_realization -> model_realization (or just realization towards the user, we are not just concerned with GEO apps?)
• <GEO_ID> - > <STATIC_MODEL_ID> or <MODEL_REALIZATION_ID>

(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 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

[codspeed-hq]

CodSpeed Performance Report

Merging #9820 will not alter performance

_{Comparing StephanDeHoop:add_dev_documentation_on_everest_vs_ert_data_models (b0302e4) with main (210f25b)}

Summary

✅ 25 untouched benchmarks

[verveerpj]

In principle correct. But some amendments.

[verveerpj]

Just a general remark: I am not happy with the use of geo, <GEO> and geo realization. That ties the optimizer unnecessarily to geological applications. Considering that the domain should (at least) be energy / energy transition, we should probably be consistent and talk about model realizations rather than geo realizations.

[StephanDeHoop]

Just a general remark: I am not happy with the use of geo, <GEO> and geo realization. That ties the optimizer unnecessarily to geological applications. Considering that the domain should (at least) be energy / energy transition, we should probably be consistent and talk about model realizations rather than geo realizations.

Yes I completely agree, that's why I suggested in the description of the PR to change this name. However, since it is not changed in the code yet, I thought we should be consistent with what we currently have until we decide on a better name, like model_realizations (and MODEL_ID instead of GEO_ID). If you think it's OK to name it already then I'll do that and make another quick PR doing this name change (at least in the code, we can then think about if we should also rename the actual folder name to where we write the output).

[yngve-sk]

Nice job, I think this looks really nice now, and feel like someone new to Everest/ERT could read this and get a better idea of what's going on. LGTM, I left some smaller comments I think you can address before merging.