core: improve stdcm heuristic using actual remaining distance

[eckter]

Fix #6605

The implementation could be improved in some ways but it seems good enough and simple enough for now.

Average execution time is divided by roughly 2, same for std.
Execution time goes slightly up for the fastest requests.

Only one request goes above 100s now, it reaches the timeout limit (120s) but actually stops naturally with a "no path found" just before the exception would be raised.

The preprocessing only takes ~ 5% of the execution time, so we have quite a lot of margin to improve it further later on.

Benchmark on realistic requests (everything is in seconds, describe is from pandas):

old.time.describe()

count 303.000000
mean 8.215783
std 20.534878
min 1.708356
25% 1.905426
50% 2.161869
75% 3.846870
max 123.005467
Name: time, dtype: float64

new.time.describe()

count 303.000000
mean 4.904902
std 11.438471
min 1.705818
25% 2.036432
50% 2.208790
75% 2.850309
max 120.813108
Name: time, dtype: float64

(new.time - old.time).describe()

count 303.000000
mean -3.310882
std 14.979293
min -120.109074
25% -0.550600
50% -0.024111
75% 0.159067
max 33.703450
Name: time, dtype: float64

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 94.73684% with 5 lines in your changes are missing coverage. Please review.

Project coverage is 29.39%. Comparing base (f6e3e93) to head (0a5742b).

Files	Patch %	Lines
...cf/osrd/stdcm/graph/EngineeringAllowanceManager.kt	33.33%	0 Missing and 2 partials ⚠️
.../src/main/kotlin/fr/sncf/osrd/graph/Pathfinding.kt	50.00%	0 Missing and 1 partial ⚠️
...c/main/kotlin/fr/sncf/osrd/stdcm/STDCMHeuristic.kt	98.73%	0 Missing and 1 partial ⚠️
.../main/kotlin/fr/sncf/osrd/stdcm/graph/STDCMEdge.kt	0.00%	1 Missing ⚠️

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Additional details and impacted files

@@            Coverage Diff            @@
##                dev    #7417   +/-   ##
=========================================
  Coverage     29.38%   29.39%           
+ Complexity     2012     2008    -4     
=========================================
  Files          1173     1174    +1     
  Lines        145276   145356   +80     
  Branches       2828     2845   +17     
=========================================
+ Hits          42693    42730   +37     
- Misses       100917   100957   +40     
- Partials       1666     1669    +3     

Flag	Coverage Δ
core	75.06% <94.73%> (-0.14%)	⬇️
editoast	72.41% <ø> (-0.03%)	⬇️
front	9.80% <ø> (ø)
gateway	2.41% <ø> (ø)
railjson_generator	87.49% <ø> (ø)
tests	83.96% <ø> (ø)

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[Erashin]

Good job.