Rewrite run context to python only

[oyvindeide]

Issue
#my_issue

Approach
Short description of the approach

Pre review checklist

• Added appropriate release note label
• PR title captures the intent of the changes, and is fitting for release notes.
• Commit history is consistent and clean, in line with the contribution guidelines.

Adding labels helps the maintainers when writing release notes. This is the list of release note labels.

[codecov-commenter]

Codecov Report

Merging #3649 (bffc37f) into main (240983f) will increase coverage by 0.06%.
The diff coverage is 73.01%.

@@            Coverage Diff             @@
##             main    #3649      +/-   ##
==========================================
+ Coverage   64.44%   64.51%   +0.06%     
==========================================
  Files         592      590       -2     
  Lines       46386    46157     -229     
  Branches     4186     4161      -25     
==========================================
- Hits        29895    29776     -119     
+ Misses      15141    15038     -103     
+ Partials     1350     1343       -7     

Impacted Files	Coverage Δ
src/ert_shared/models/base_run_model.py	77.60% <ø> (+0.82%)	⬆️
src/libres/lib/enkf/enkf_state.cpp	25.20% <ø> (+0.30%)	⬆️
src/libres/lib/enkf/ensemble_config.cpp	46.84% <ø> (+0.08%)	⬆️
src/res/enkf/enkf_simulation_runner.py	97.05% <ø> (+1.34%)	⬆️
src/res/enkf/enums/__init__.py	100.00% <ø> (ø)
src/libres/lib/enkf/enkf_main.cpp	30.44% <6.25%> (-0.38%)	⬇️
src/res/enkf/run_arg.py	87.27% <83.33%> (+5.45%)	⬆️
src/res/enkf/ert_run_context.py	96.82% <97.05%> (+1.58%)	⬆️
src/libres/lib/enkf/run_arg.cpp	72.46% <100.00%> (-6.49%)	⬇️
src/res/enkf/enkf_main.py	89.02% <100.00%> (-0.05%)	⬇️
... and 9 more

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[eivindjahren]

This is a massive improvement, but we should keep going in this direction as there is so much more to be cleaned up! I suggest creating a PR investigating this straight away.

[oyvindeide]

test this please