core: pathfinding: log a little extra info about failures

[eckter]

We barely logged anything on pathfindings. We now log:

1. success
2. no path found at all, including the last reached waypoint index
3. no path found because of [constraint type / error type]

Not much, but it can still help

This PR also fixes the "couldn't find route" error, it had an irrelevant type.

[codecov-commenter]

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Codecov Report

Attention: Patch coverage is 86.66667% with 2 lines in your changes missing coverage. Please review.

Project coverage is 36.90%. Comparing base (c2b8718) to head (335c785).
Report is 13 commits behind head on dev.

Files with missing lines	Patch %	Lines
.../kotlin/fr/sncf/osrd/sim_infra/utils/InfraUtils.kt	0.00%	1 Missing ⚠️
.../api_v2/pathfinding/PathfindingBlocksEndpointV2.kt	83.33%	1 Missing ⚠️

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Additional details and impacted files

@@             Coverage Diff              @@
##                dev    #8769      +/-   ##
============================================
- Coverage     36.91%   36.90%   -0.01%     
  Complexity     2208     2208              
============================================
  Files          1255     1255              
  Lines        114115   114126      +11     
  Branches       3188     3188              
============================================
+ Hits          42120    42122       +2     
- Misses        70100    70109       +9     
  Partials       1895     1895              

Flag	Coverage Δ
core	74.75% <86.66%> (+0.02%)	⬆️
editoast	72.04% <ø> (-0.04%)	⬇️
front	14.92% <ø> (ø)
gateway	2.20% <ø> (ø)
osrdyne	2.71% <ø> (ø)
railjson_generator	87.49% <ø> (ø)
tests	86.45% <ø> (ø)

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[bougue-pe]

LGTM (feel free to resolve comment)