net: add UDP listen, resolver, DNSError, and TCP listener APIs for wasm (#63)

* net: add UDP listen, resolver, DNSError, and TCP listener APIs for wasm

TinyGo's net package was missing several symbols that upstream Go's
js/wasm net declares, blocking builds that pull pion/transport, pion/dtls,
and similar (via netbird's WASM client). Add them, backed by the existing
netdev abstraction so they compile for all targets and no-op cleanly under
nopNetdev (matching Go's js runtime behavior):

- DNSError type (dnserror.go), copied from Go 1.26.2.
- Resolver + DefaultResolver with LookupHost/LookupIP/LookupIPAddr/
  LookupNetIP/LookupPort; LookupHost/LookupIP package funcs; Dialer.Resolver
  field for API compatibility.
- UDPConn: ListenUDP, ReadFromUDP(AddrPort), WriteToUDP(AddrPort),
  SetReadBuffer, SetWriteBuffer.
- TCPConn: CloseRead, SetNoDelay, SetReadBuffer, SetWriteBuffer,
  ReadFrom(io.Reader).
- TCPListener: ListenTCP, AcceptTCP, SetDeadline; ListenPacket package func.
- Interface: Addrs, MulticastAddrs stubs.

* more complete PR for adding more net support (#64)

* format unixsock

dial.go

@@ -87,6 +87,13 @@ type Dialer struct {
 	// If KeepAliveConfig.Enable is false and KeepAlive is negative,
 	// keep-alive probes are disabled.
 	KeepAliveConfig KeepAliveConfig
+
+	// Resolver optionally specifies an alternate resolver to use.
+	//
+	// TINYGO: present for API compatibility; DialContext resolves via the
+	// netdev-backed ResolveTCPAddr/ResolveUDPAddr and does not consult this
+	// field.
+	Resolver *Resolver
 }
 
 // Dial connects to the address on the named network.
@@ -281,3 +288,22 @@ func Listen(network, address string) (Listener, error) {
 
 	return listenTCP(laddr)
 }
+
+// ListenPacket announces on the local network address.
+//
+// TINYGO: only UDP networks are supported, backed by ListenUDP; the
+// returned PacketConn is a *UDPConn.
+func ListenPacket(network, address string) (PacketConn, error) {
+	switch network {
+	case "udp", "udp4":
+	default:
+		return nil, fmt.Errorf("Network %s not supported", network)
+	}
+
+	laddr, err := ResolveUDPAddr(network, address)
+	if err != nil {
+		return nil, err
+	}
+
+	return ListenUDP(network, laddr)
+}