JSON Schema validation is not working

[acl-cqc]

On main, this test added to hugr-core/src/hugr/serialize/test.rs passes:

#[test]
fn not_a_hugr() {
    let val = serde_json::Value::from("Hello, world!");
    NamedSchema::check_schemas(&val, get_testing_schemas(true));
}

Clearly it shouldn't! Adding this to testing_hugr_schema_live.json causes the schema violation to be detected (similarly for testing_hugr_schema_strict_live.json):

"$ref": "#/$defs/TestingHugr"

....but, lo, there are a bunch of other new failures in:

    hugr::serialize::test::proptest::prop_roundtrip_opdef
    hugr::serialize::test::proptest::prop_roundtrip_optype
    hugr::serialize::test::proptest::prop_roundtrip_poly_func_type
    hugr::serialize::test::proptest::prop_roundtrip_type
    hugr::serialize::test::proptest::prop_roundtrip_value

Moreover, the "non-testing" schemas will also need some kind of update - I conjecture possibly "$ref": "#/$defs/Package" (or a oneOf including package and SerialHugr?)

[acl-cqc]

I've pushed branch acl/schema_test which includes

• The update of the "testing" schemas (which triggers all those prop_roundtrip failures)...however note we should do this via scripts/generate_schemas.py so it is not lost on the next regeneration
• A new test which checks adding/removing fields from a valid testing json triggers the errors we expect