Support copying an Instance

I've encountered some proxy-wasm modules (https://github.com/corazawaf/coraza and https://higress.cn/en/docs/latest/plugins/ai/api-o11y/geo-ip/) which do large amount of initialization work. Since the modules are not thread safe, if I want to be able to concurrently use the module, I would need to create multiple instances of the module. But since the initialization is so heavy, this would really slowdown the system. It would be nice if you could initialize one module and then copy it as needed for each concurrent thread.