Update dependencies, fix pydantic-core usage, fix CI issues

[dmontagu]

• Update pydantic-core to 2.6.0
  • The main changes in pydantic required were changes to handling of union schemas to handle the case where the choices field might have labels. I have not added tests for this, just gotten the code to type-check. I think we can add tests when we expose this functionality into pydantic somehow.
• Update all other dependencies (I just ran make refresh-lockfiles). This included pyright and ruff, which resulted in needing to change some stuff for type-checking/linting.
  • While addressing updates to pyright's type checking, I noticed that we no longer need to check for indirect schema references in the tagged union schema, so I removed that code.
• Fix the pydantic test that has been causing the pydantic-core CI to fail due to updated type serialization. (It was failing because it was checking that two instances of type str that were equal were actually the same object in memory, which clearly isn't guaranteed. It wasn't unreasonable to want them to be the same, because they were previously both the exact str instance FooEnum.FOO.value, but anyway I don't think it should be required and I changed the test to just check the types were exactly the same and the values were equal).

Selected Reviewer: @lig

[cloudflare-pages]

Deploying with    Cloudflare Pages

Latest commit:	1aa2d46
Status:	✅  Deploy successful!
Preview URL:	https://1575e8df.pydantic-docs2.pages.dev
Branch Preview URL:	https://use-pydantic-core-2-6-0.pydantic-docs2.pages.dev

View logs

[dmontagu]

please review