FEAT Breaking: Registry protocol + ScorerRegistry

[rlundeen2]

Refactored registry logic into a shared pyrit.registry module and added a new ScorerRegistry for managing pre-configured scorer instances.

Changes

• Abstracted common registry patterns into registry module with base classes for class registries (Type[T]) and instance registries (pre-configured objects)
• Migrated ScenarioRegistry and InitializerRegistry to inherit from BaseClassRegistry
• Added ScorerRegistry extending BaseInstanceRegistry for managing scorer instances
• Added documentation in registry with overview and usage examples

[romanlutz]

Unsurprisingly, I like practically everything about this 😆

[ValbuenaVC]

The only thing I think we may want to add before merging is encoding/decoding logic for registries. The protocol choice is fantastic, but it requires every registry to store classes or instances differently. Aside from that looks great!