Decoupled ScenarioMetadata and InitializerMetadata from Identity by introducing RegistryEntry

[bashirpartovi]

Summary

Replaces Identifier with a new lightweight RegistryEntry dataclass as the base for ScenarioMetadata and InitializerMetadata. Registry metadata no longer carries Identifier-specific fields like hash, identifier_type, unique_name, or pyrit_version, keeping the registry layer focused on class discovery and lookup.

Motivation

Identifier includes hash computation, versioning, and storage-related metadata that are irrelevant for class registry entries. Using a minimal RegistryEntry base:

• Reduces coupling between the registry and identity systems
• Removes unnecessary fields from metadata objects
• Makes the registry metadata contract explicit and minimal

Context

Please see #1369

[rlundeen2]

Looks great! TY for thinking about this!