feat: replace InterfaceFilter with ForwardRequirements, add WildcardListener, complete alpha.20 bump

- Replace DynInterfaceFilter with ForwardRequirements for per-IP forward
  precision with source-subnet iptables filtering for private forwards
- Add WildcardListener (binds [::]:port) to replace the per-gateway
  NetworkInterfaceListener/SelfContainedNetworkInterfaceListener/
  UpgradableListener infrastructure
- Update forward-port script with src_subnet and excluded_src env vars
- Remove unused filter types and listener infrastructure from gateway.rs
- Add availablePorts migration (IdPool -> BTreeMap<u16, bool>) to alpha.20
- Complete version bump to 0.4.0-alpha.20 in SDK and web

core/src/bins/tunnel.rs

@@ -13,7 +13,7 @@ use visit_rs::Visit;
 
 use crate::context::CliContext;
 use crate::context::config::ClientConfig;
-use crate::net::gateway::{Bind, BindTcp};
+use tokio::net::TcpListener;
 use crate::net::tls::TlsListener;
 use crate::net::web_server::{Accept, Acceptor, MetadataVisitor, WebServer};
 use crate::prelude::*;
@@ -57,7 +57,12 @@ async fn inner_main(config: &TunnelConfig) -> Result<(), Error> {
                             if !a.contains_key(&key) {
                                 match (|| {
                                     Ok::<_, Error>(TlsListener::new(
-                                        BindTcp.bind(addr)?,
+                                        TcpListener::from_std(
+                                            mio::net::TcpListener::bind(addr)
+                                                .with_kind(ErrorKind::Network)?
+                                                .into(),
+                                        )
+                                        .with_kind(ErrorKind::Network)?,
                                         TunnelCertHandler {
                                             db: https_db.clone(),
                                             crypto_provider: Arc::new(tokio_rustls::rustls::crypto::ring::default_provider()),