chore: Update jsonschema usage

[Stranger6667]

Hey!

This PR updates some usages of the jsonschema crate including the recent meta API which is dedicated to meta-schema validation (and is substantially faster than creating a new validator via Validator::new). Also, validation_error_into_owned is not needed anymore, as Validator::new returns ValidationError<'static> + there is the ValidationError::to_owned method which does exactly what validation_error_into_owned was doing.

Another small detail is that I've noticed that the actual validation error is ignored in JsonColumnMetadata::validate, so I replaced it with is_valid which is usually significantly faster for invalid instances.

[ignatz]

Much appreciated, thank you!