json.schema() generates non-serializable default values #1182

Description

msgspec.json.schema() puts a raw set() / bytearray() object into the schema's default for Struct fields using default_factory=set or default_factory=bytearray, so the result isn't json-serializable:

import json

import msgspec
from msgspec import field


class Config(msgspec.Struct):
    features: set[str] = field(default_factory=set)


json.dumps(msgspec.json.schema(Config))
# TypeError: Object of type set is not JSON serializable

I would expect the default to be a json value (e.g. []), like it already is for default_factory=list/dict.