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

interface.go

@@ -35,6 +35,22 @@ type Interface struct {
 	Flags        Flags        // e.g., FlagUp, FlagLoopback, FlagMulticast
 }
 
+// Addrs returns a list of unicast interface addresses for a specific
+// interface.
+//
+// TINYGO: not implemented; netdev exposes no per-interface address list.
+func (ifi *Interface) Addrs() ([]Addr, error) {
+	return nil, errors.New("Interface.Addrs not implemented")
+}
+
+// MulticastAddrs returns a list of multicast, joined group addresses
+// for a specific interface.
+//
+// TINYGO: not implemented; netdev exposes no per-interface address list.
+func (ifi *Interface) MulticastAddrs() ([]Addr, error) {
+	return nil, errors.New("Interface.MulticastAddrs not implemented")
+}
+
 type Flags uint
 
 const (
@@ -93,3 +109,8 @@ func InterfaceAddrs() ([]Addr, error) {
 func InterfaceByIndex(index int) (*Interface, error) {
 	return nil, errors.New("InterfaceByIndex not implemented")
 }
+
+// InterfaceByName returns the interface specified by name.
+func InterfaceByName(name string) (*Interface, error) {
+	return nil, errors.New("InterfaceByName not implemented")
+}