Handle overlapping electrification

Description

We should handle overlapping electrification (Here is an example in London https://en.wikipedia.org/wiki/Railway_electrification#Fourth_rail, we can find a lot of cases in Europe).
Also relates to https://github.com/osrd-project/osrd/issues/5957.

Acceptance criteria

• Overlapping electrification should not trigger a warning (except if they're of the same electrification type)
• Pathfinding, simulation and STDCM should handle this overlapping. Currently, core arbitrarily selects one electrification in case of overlapping.
• OSM Import should handle it creating one object per electrification type.

Question

What should we do when a train that supports several signaling systems uses a track that also supports several of its electrifications? (which effort curve to choose?)

Technical Design

• Adapt editoast error generation
• Adapt core
  • Internal infra representation
  • Pathfinding
  • Simulation
  • STDCM
  • Adapt electrical profile use
• Adapt editoast osm import

Start with the technical-design checklist and the existing core internal infrastructure representation, then trace pathfinding, simulation, STDCM, electrical-profile use, editoast error generation, and editoast OSM import. Done means overlapping electrification is accepted without same-type warnings, supported across the listed core workflows, and imported as one object per electrification type; the effort-curve question still needs a decision.