core: trains cannot see a signal before passing the previous one

[Khoyo]

Fixes #4923.

[codecov]

Codecov Report

Merging #4924 (eeb504c) into dev (cea50f8) will increase coverage by 0.00%.
Report is 2 commits behind head on dev.
The diff coverage is 100.00%.

@@            Coverage Diff            @@
##                dev    #4924   +/-   ##
=========================================
  Coverage     22.35%   22.36%           
- Complexity     2276     2278    +2     
=========================================
  Files           863      863           
  Lines         90282    90286    +4     
  Branches       2324     2326    +2     
=========================================
+ Hits          20184    20188    +4     
  Misses        68821    68821           
  Partials       1277     1277           

Flag	Coverage Δ
core	79.69% <100.00%> (+<0.01%)	⬆️

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Files Changed	Coverage Δ
...f/osrd/standalone_sim/ScheduleMetadataExtractor.kt	89.27% <100.00%> (+0.11%)	⬆️