Panic on parsing server config URLs

[link2xt]

There are multiple places where parsing server config from URL or just trying to parse a password panics and crashes the whole application using the library.

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

Lines 436 to 442 in c52b77d

	panic!(
	"{} is expecting a {} bytes key, but password: {} ({} bytes after decode)",
	method,
	enc_key.len(),
	password,
	v.len()
	);

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

Line 447 in c52b77d

panic!("{method} password {password} is not base64 encoded, error: {err}");

(triggered by ServerConfig::from_url("ss://2022-blake3-aes-128-gcm:XYZ@127.0.0.1:9999"))

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

Line 518 in c52b77d

let upsk = split_iter.next().expect("uPSK");

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

Line 529 in c52b77d

panic!("iPSK {ipsk} is not base64 encoded, error: {err}");

One of the cases was fixed in #1762

[link2xt]

let upsk = split_iter.next().expect("uPSK"); is still not fixed.

[zonyitoo]

It shouldn't fail. It would always be Some(..).