Upgrade or remove pydantic dependency

### What's needed?

[pydantic](https://docs.pydantic.dev/latest/) has a new major release.

### Proposed solution

We need to either upgrade or remove the dependency, as we'll also use [marshmallow](https://marshmallow.readthedocs.io/en/stable/) too and there is a lot of overlap.

### Use cases

_No response_

### Alternatives and workarounds

_No response_

### Additional context

_No response_