[Rust] Release 0.58.0

Added

• backend = Pyo3 on #[jsonschema::validator], generating a validator that reads Python objects in place.
• backend = Magnus on #[jsonschema::validator], generating a validator that reads Ruby objects in place.
• jsonschema::meta::pyo3, the bundled meta-schema validators for a schema held as a Python object.
• jsonschema::meta::magnus, the bundled meta-schema validators for a schema held as a Ruby object.
• methods = { ... } on #[jsonschema::validator], selecting which of is_valid, validate, and iter_errors are generated.
• json::Jsonb, validating a Postgres jsonb value in place, behind the jsonb feature.

Performance

• oneOf and anyOf whose branches each require a property fixed to a distinct string validate only the branch matching the instance's value.
• Generated validate checks required in the same pass over an object as properties, instead of looking up each required name.

Fixed

• A oneOf over $ref branches beside a sibling none of them admits, which canonicalized to an allOf instead of false.
• multipleOf incorrectly accepted 1e-400 and other magnitudes below the smallest f64 subnormal with arbitrary-precision (they are not zero).
• Numeric keywords panicked on a custom representation holding a number past f64 without arbitrary-precision.