Cyclical "is-a" relationships between types causes StackOverflowException

[popematt]

When any number of types have a circular "is-a" relationship it results in a StackOverflowException during validation. Ideally, it should result in an InvalidSchemaException when loading the schema. See amazon-ion/ion-schema-rust#205 for more details.

Minimal reproducible example:

@Test
fun `types with cyclical is-a relationships should cause InvalidSchemaException`() {
    val iss = IonSchemaSystemBuilder.standard().build()
    val isl = """
        type::{ name: a, type: b }
        type::{ name: b, type: a }
    """
    assertThrows<InvalidSchemaException> { iss.newSchema(isl) }
}