add pydantic-v2 model

[glass-ships]

I'd like to start doing some testing and convert to Pydantic V2 in a number of @monarch-initiative projects, now that it's finally released, stable, and compatible with Python >=3.7.

• Adds a Make target for pydantic-v2
• Updates linkml to a more recent version which (I believe) includes changes to pydantic-generator to allow this

I did not however add any tests against the generated model, wasn't quite sure what that would look like

[glass-ships]

As a side note, I considered making the v2 model just biolink.pydanticmodel and the v1 model biolink.pydanticmodel_v1 to keep with pydantic's own naming scheme, but it seems like that might be a breaking change for anyone currently expecting pydantic v1.