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

dnserror.go

@@ -0,0 +1,47 @@
+// TINYGO: The following is copied and modified from Go 1.26.2 official implementation.
+
+// Copyright 2018 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package net
+
+// DNSError represents a DNS lookup error.
+type DNSError struct {
+	UnwrapErr   error  // error returned by the [DNSError.Unwrap] method, might be nil
+	Err         string // description of the error
+	Name        string // name looked for
+	Server      string // server used
+	IsTimeout   bool   // if true, timed out; not all timeouts set this
+	IsTemporary bool   // if true, error is temporary; not all errors set this
+
+	// IsNotFound is set to true when the requested name does not
+	// contain any records of the requested type (data not found),
+	// or the name itself was not found (NXDOMAIN).
+	IsNotFound bool
+}
+
+// Unwrap returns e.UnwrapErr.
+func (e *DNSError) Unwrap() error { return e.UnwrapErr }
+
+func (e *DNSError) Error() string {
+	if e == nil {
+		return "<nil>"
+	}
+	s := "lookup " + e.Name
+	if e.Server != "" {
+		s += " on " + e.Server
+	}
+	s += ": " + e.Err
+	return s
+}
+
+// Timeout reports whether the DNS lookup is known to have timed out.
+// This is not always known; a DNS lookup may fail due to a timeout
+// and return a [DNSError] for which Timeout returns false.
+func (e *DNSError) Timeout() bool { return e.IsTimeout }
+
+// Temporary reports whether the DNS error is known to be temporary.
+// This is not always known; a DNS lookup may fail due to a temporary
+// error and return a [DNSError] for which Temporary returns false.
+func (e *DNSError) Temporary() bool { return e.IsTimeout || e.IsTemporary }