Unable to Distinguish Connection Refusal Source in `connect_raw`

[eval-exec]

Hello,

https://github.com/dizda/fast-socks5/blob/e64cdbcc8d643380adbf5c3bf6f35ab653940791/src/client.rs#L606-L638

The connect_raw method currently can't differentiate between connection refusals that originate from the proxy server itself (e.g., proxy server is down) and those from the target server (e.g., target service is unreachable). This distinction would be valuable for debugging and error handling. Is there a way to enhance error reporting to provide more detailed information about the source of the refusal?