Add possibility to read rft observations from csv file

[HakonSohoel]

Approach
Introduce the possibility to read rft observations as a csv file.
The csv file is on the same format currently in use with the GENDATA_RFT forward model.

• 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')

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 90.53%. Comparing base (87e6aa7) to head (acddbb9).
⚠️ Report is 13 commits behind head on main.
✅ All tests successful. No failed tests found.

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #12628      +/-   ##
==========================================
- Coverage   90.54%   90.53%   -0.01%     
==========================================
  Files         435      434       -1     
  Lines       30014    30038      +24     
==========================================
+ Hits        27175    27195      +20     
- Misses       2839     2843       +4     

Flag	Coverage Δ
cli-tests	37.40% <37.03%> (+0.13%)	⬆️
gui-tests	68.90% <51.85%> (+0.19%)	⬆️
performance-and-unit-tests	73.92% <100.00%> (+0.03%)	⬆️
test	38.03% <25.92%> (-0.02%)	⬇️

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[Copilot]

Copilot encountered an error and was unable to review this pull request. You can try again by re-requesting a review.

[codspeed-hq]

CodSpeed Performance Report

Merging this PR will not alter performance

_{Comparing read-rft-obs-from-csv-file (acddbb9) with main (67f7ea4)}

Summary

✅ 22 untouched benchmarks

[Copilot]

Pull request overview

Copilot reviewed 3 out of 3 changed files in this pull request and generated 9 comments.

[eivindjahren]

Just have a look at whether any of the copilot suggestions make sense to apply, otherwise I have no comments.