migrate pydantic

[robsdavis]

Description

This branch migrates from pydantic version 1.X to 2.X. This requires significant changes to the schema and distribution classes (core classes in synthcity's logic).
This closes #296.
Minor point: We also abstract n_folds to close #280.

Main changes

• distribution class
  • Update _validate_marginal_distribution to accept FieldValidationInfo type for values parameter
  • Handle random sampling using new PrivateAttr _rng. Implemented new initialize_rng function to enable this
  • Updated validation throughout
  • New PassThroughDistribution
• Automated updates to validation decorators
  • tabular_encoder, constraints
• Allow plugin to handle protected column explicitly using PassThroughDistribution
• Schema class
  • Completely re-written with new validation
  • New _infer_domain method
• Update tests to work with updated classes
  • test_schema
  • test_distribution

Affected Dependencies

Removed the version pin on pydantic

How has this been tested?

The standard battery of tests, but with some small changes to the tests to make them compatible with new logic.

Checklist

• I have followed the Contribution Guidelines and Code of Conduct
• I have commented my code following the van der Schaar Lab Styleguide
• I have labelled this PR with the relevant Type labels
• My changes are covered by tests