Rework errors

[Stranger6667]

• Avoid lifetimes. There is already Arc inside validators, this might be a way to avoid refs to the schema.
• Rename validate to iter_errors and add validate that will return the first error

[hoijui]

I am here mainly for the second part (Owned version of errors). without this, I do not know how to wrap ValidationError within my own thiserror enum. I Can get it to work somehow, but It would be a lot of lines of code.
(I am still a rust newb)

[Stranger6667]

@hoijui There is a pub(crate) to_owned function which surely could be replaced by the ToOwned implementation - though, I am not yet sure if it will be sufficient. Let me know if I can help