feat(core): metadata handling of manifests

[Dacksus]

trafficstars

• adds separation of functional description and metadata of nodes and edges for dialogues
• adds separation of functional description and metadata of models for protocols
• cached protoco.digest to avoid unnecessary recomputation

note: Models can't have fields that are named "description"!

[Dacksus]

updated model digestion (to use pydantic v2). -> Needs refactoring throughout the framework to update deprecated function calls (see tests)