Remove history observations

[yngve-sk]

Goes with equinor/semeio#860
PS: Merge after 2026 January branching out
No usages by non-SCOUT users since september

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 90.47%. Comparing base (a29328d) to head (c3e6043).
⚠️ Report is 28 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #12611      +/-   ##
==========================================
- Coverage   90.55%   90.47%   -0.08%     
==========================================
  Files         435      435              
  Lines       29940    29948       +8     
==========================================
- Hits        27112    27096      -16     
- Misses       2828     2852      +24     

Flag	Coverage Δ
cli-tests	37.29% <100.00%> (-0.06%)	⬇️
gui-tests	68.67% <100.00%> (+<0.01%)	⬆️
performance-and-unit-tests	73.79% <100.00%> (-0.13%)	⬇️
test	38.08% <50.00%> (-0.02%)	⬇️

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[codspeed-hq]

Merging this PR will not alter performance

✅ 22 untouched benchmarks

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_{Comparing yngve-sk:26.01.remove-history-obs (c3e6043) with main (fcad14a)}

[andreas-el]

🎖️