Alpha 5: configuration

Mostly changes around the component API:

• use Pydantic models for configuration
• update Trainable interface to take training options
• add iterative training interface

What's Changed

• Use Pydantic models for component configurations by @mdekstrand in #596
• Re-add return type variable for Component by @mdekstrand in #598
• Migrate HPF to configuration object and fix BiasConfig serialization by @mdekstrand in #600
• Move Trainable interface and add TrainingOptions by @mdekstrand in #599
• Add iterative training API by @mdekstrand in #601
• rename "Lenskit" to LensKit for consistency by @mdekstrand in #602

Full Changelog: v2025.0.0a4...v2025.0.0a5