editoast: train schedule exceptions payload refactor

[Wadjetz]

Fallow up from PR comment

This PR refactor exceptions change groups structure

[github-actions]

⚠️ API changes

This Pull Request introduces some changes in the API:

• please own it: notify or even prepare dedicated PR(s) to consumer projects

Changes in Schemas

Dear @Wadjetz, please ensure the following:

• changes should match in osrd_schemas and editoast schemas
• the RailJSON version in osrd_schemas::infra.py and editoast schemas::infra::railjson.rs should match and be bumped on any change of infra schemas (same goes for rolling-stock between osrd_schemas::rolling_stock.py and editoast schemas::rolling_stock.rs)
• the version of the Python package in osrd_schemas::pyproject.toml should be bumped on any change