`ServerConfig::from_url` panics instead of returning an error on unknown method

[link2xt]

The problem is this line:

shadowsocks-rust/crates/shadowsocks/src/config.rs

Line 908 in 78739f8

let method = method.parse().expect("method");

For an example of URL that causes panic: ss://foo:bar@127.0.0.1:9999.

Downstream issue: chatmail/core#6189

Bugfix: #1762