editoast: add CLI to import towed rolling stock

[woshilapin]

Closes #8668

This new CLI brings a simple way to import Towed rolling stock in the DB from JSON files, without the need to start the editoast web service.

[codecov-commenter]

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Codecov Report

Attention: Patch coverage is 97.91667% with 1 line in your changes missing coverage. Please review.

Project coverage is 42.53%. Comparing base (0e1ea9b) to head (d838e73).
Report is 8 commits behind head on dev.

Files with missing lines	Patch %	Lines
editoast/src/client/import_rolling_stock.rs	97.91%	1 Missing ⚠️

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Additional details and impacted files

@@             Coverage Diff              @@
##                dev    #9580      +/-   ##
============================================
+ Coverage     42.51%   42.53%   +0.02%     
  Complexity     2271     2271              
============================================
  Files          1311     1311              
  Lines        105413   105444      +31     
  Branches       3297     3297              
============================================
+ Hits          44812    44849      +37     
+ Misses        58655    58649       -6     
  Partials       1946     1946              

Flag	Coverage Δ
core	75.05% <ø> (ø)
editoast	73.75% <97.91%> (+0.04%)	⬆️
front	18.79% <ø> (ø)
gateway	2.19% <ø> (ø)
osrdyne	3.28% <ø> (ø)
railjson_generator	87.49% <ø> (ø)
tests	86.74% <ø> (ø)

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[leovalais]

LGTM, thanks!