core: conflict detection: add start and end of resource usage in the response of the V2 conflict detection endpoint

[Erashin]

Description

Add resource start and end info to conflict detection response payload.

Goal

Being able to communicate thos info to the front end

AC

• [ ] The ressource start and end info have been added to conflict detection response payload (as well as on the editoast side).

[Erashin]

This info has been added to conflict requirements in this issue https://github.com/OpenRailAssociation/osrd/issues/8680.