New VOCS Pydantic object

[ChristopherMayes]

This introduces a Pydantic object VOCS and associated ConstraintEnum and ObjectiveEnum objects for better validation.

• All internal code, tests, and examples updated.
• new example notebook: https://github.com/ChristopherMayes/Xopt/blob/new_vocs/examples/basic/vocs.ipynb
• Solves issues with floats in YAML being parsed as str
• drop-in replacement to internals.
• vocs["variables"] -> getattr(vocs, "variables") is needed in some places. Such code should be refactored.