V2: replace URL types with a 3rd party library

[samuelcolvin]

As per #4470, the URL types - everything inheriting from AnyUrl are messed up, it may just be weird edge cases that don't work, but getting URLs to be validated correct is a really hard task and shouldn't be included in pydantic.

In V2, we should use a 3rd party library for URL parsing and validation, ideally in rust as part of pydantic-core.

[samuelcolvin]

Also #1665 - remove user_required.

[commonism]

I can recommend yarl.URL

[samuelcolvin]

This is done, we're using the URL crate from rust.