Replace use of GraphUrl with url::Url in graph-codegen

[sreeise]

The GraphUrl in graph-http is no longer used in any of the main client code, not 100% sure though. Either way the use of GraphUrl in graph-codegen, and if its used anywhere else, needs to be replaced with url::Url which is a crate in the Rust ecosystem and used in this crate almost everywhere. Its what GraphUrl uses internally.

If there is specific funtionallity of GraphUrl that is needed for codegen, and that is not already part of url::Url, we should consider creating an ext trait in graph-codegen and an impl of that trait for url::Url.