LMR: relaunch initial pathfinding to validate path when changing traction engine length

[Erashin]

What happened?

In LMR, the initial pathfinding launched to validate the path depends on the length of the rolling-stock. However, modifying the length of the initial consist does not re-launch a pathfinding to validate the path.

What did you expect to happen?

Changing the length of the initial consist should re-launch a validation pathfinding request (this might be linked to this issue).

BONUS (and this is independant from the issue quoted just above, this is a bug regardless and should probably be fixed if possible):
some fields re-launch a validation pathfinding request when they shouldn't need to. If you can deactivate them easily, that'd be perfect:

• the date field of any PR in the path
• the time field of any PR in the path
• the tolerance field of any PR in the path
• the horaire précis/dès que possible field

How can we reproduce it (as minimally and precisely as possible)?

1. Open LMR
2. Fill out a consist
3. Press F12 and open console -> Réseau
4. Make a path: the pathfinding validation is launched: you see pathfindingBlocks requests being sent out
5. Change the length of the initial consist
6. Check console: no additional pathfindingBlocks requests were sent out

On which environments the bug occurs?

Local

On which browser the bug occurs?

Firefox

OSRD version (top right corner Account button > Informations)

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