Harmonize layers data

[SharglutDev]

Description and goal

To facilitate the management of layers in osrd-ui, we should harmonize their data in this repo.

We should follow the model of conflicts type :

export type Conflict = {
    timeStart: number;
    timeEnd: number;
    spaceStart: number;
    spaceEnd: number;
};

Merging this issue will allow to remove some TODO in ManchetteWithSpaceTimeChart.tsx in osrd repo.

Acceptance criteria

All current layers follow this model :

• Path
• Occupancy block
• Work schedules

[emersion]

Note, it appears the PathLayer data has been formatted this way (in two separate arrays) to follow data-oriented design principles. In theory it should be easier on the memory allocator and CPU cache when handling lots of trains with many data points. I haven't verified that this is the case in practice (maybe not because of JavaScript's memory layout?), or if it really makes a substantial difference.