Migrate from Pydantic v1 to v2

[wilbrdt]

Feature Request

Is your feature request related to a problem or unsupported use case? Please describe.
Pydantic v1 is still supported, but other dependencies such as Ralph now only supports Pydantic v2.

Describe the solution you'd like
To be able to upgrade these dependencies, we should migrate Warren from Pydantic v1 to Pydantic v2.