Add timetable import command for train schedule v2

[ElysaSrc]

Added a test fixture editoast/src/tests/train_schedules/simple_array.json

Tested with timetable creation and timetable specification.

Closes #6737

[codecov]

Codecov Report

Attention: Patch coverage is 50.00000% with 3 lines in your changes are missing coverage. Please review.

Project coverage is 28.34%. Comparing base (6d33ff6) to head (8ae74d9).
Report is 3 commits behind head on dev.

Files	Patch %	Lines
editoast/src/client/mod.rs	0.00%	3 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##                dev    #6754      +/-   ##
============================================
- Coverage     28.34%   28.34%   -0.01%     
  Complexity     2177     2177              
============================================
  Files          1047     1047              
  Lines        129444   129450       +6     
  Branches       2576     2576              
============================================
- Hits          36691    36688       -3     
- Misses        91265    91274       +9     
  Partials       1488     1488              

Flag	Coverage Δ
core	79.39% <ø> (ø)
editoast	75.88% <50.00%> (-0.04%)	⬇️
front	8.61% <ø> (ø)
gateway	2.50% <ø> (ø)
railjson_generator	87.26% <ø> (ø)
tests	83.07% <ø> (ø)

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[flomonster]

Thanks for this PR. I made some minor request changes.

Can you also add a unit test that:

• Imports the simple_array.json
• Delete the created timetable.