feat: separate zstd and faketcp into features (#1861)

* feat: separate faketcp into a feature
* fix: no need to initialize out_len
* feat: separate zstd into a feature
* clippy: remove unnecessary cast, because for unix size_t always equals usize

easytier/src/tunnel/mod.rs

@@ -15,7 +15,6 @@ use self::packet_def::ZCPacket;
 
 pub mod buf;
 pub mod common;
-pub mod fake_tcp;
 pub mod filter;
 pub mod mpsc;
 pub mod packet_def;
@@ -33,6 +32,9 @@ pub const PROTO_PORT_OFFSET: &[(&str, u16)] = &[
     ("faketcp", 3),
 ];
 
+#[cfg(feature = "faketcp")]
+pub mod fake_tcp;
+
 #[cfg(feature = "wireguard")]
 pub mod wireguard;