editoast, front: allow providing etcs_brake_params to rolling-stock web api

[bougue-pe]

front: persist etcs params when editing a rollingstock handling etcs (without this, etcs_brake_params are emptied when updating a RS with the front).

Follow-up on #10147

AC:

• ability to create a RS with etcs_brake_params via editoast's web API:
  • curl 'http://localhost:4000/api/rolling_stock?locked=false' -X POST -H 'content-type: application/json' -H 'Cookie: gateway=<blabliblo>' --data '@/<path/to>/osrd/tests/data/rolling_stocks/etcs_level2_rolling_stock.json'
  • check in PG that etcs_brake_params column is filled
• ability to update given RS without erasing etcs_brake_params:
  • change some field of the RS using the front (i.e. name, details)
  • check in PG that etcs_brake_params column is still filled

[codecov-commenter]

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Codecov Report

Attention: Patch coverage is 33.33333% with 4 lines in your changes missing coverage. Please review.

Project coverage is 81.65%. Comparing base (accd619) to head (af30b5c).
Report is 11 commits behind head on dev.

Files with missing lines	Patch %	Lines
...ents/RollingStockEditor/RollingStockEditorForm.tsx	0.00%	4 Missing ⚠️

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Additional details and impacted files

@@            Coverage Diff             @@
##              dev   #10422      +/-   ##
==========================================
+ Coverage   81.62%   81.65%   +0.03%     
==========================================
  Files        1070     1071       +1     
  Lines      105881   106112     +231     
  Branches      727      727              
==========================================
+ Hits        86428    86650     +222     
- Misses      19412    19423      +11     
+ Partials       41       39       -2     

Flag	Coverage Δ
editoast	73.71% <100.00%> (-0.04%)	⬇️
front	89.36% <0.00%> (+0.04%)	⬆️
gateway	2.18% <ø> (ø)
osrdyne	3.28% <ø> (ø)
railjson_generator	87.50% <ø> (ø)
tests	87.05% <ø> (ø)

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[clarani]

LGTM ✅