Allow use of builtin node WebSocket when available. NFS

Node v21 and up have native WebSocket support.  This change makes the
import of the external `ws` module conditional so it will only run on
older versions of node.

See #26676

Author: sbc100

src/lib/libsockfs.js

@@ -212,17 +212,13 @@ addToLibrary({
 #if SOCKET_DEBUG
             dbg(`websocket: connect: ${url}, ${subProtocols.toString()}`);
 #endif
-            // If node we use the ws library.
-            var WebSocketConstructor;
 #if ENVIRONMENT_MAY_BE_NODE
-            if (ENVIRONMENT_IS_NODE) {
-              WebSocketConstructor = /** @type{(typeof WebSocket)} */(require('ws'));
-            } else
-#endif // ENVIRONMENT_MAY_BE_NODE
-            {
-              WebSocketConstructor = WebSocket;
+            // If node we use the ws library.
+            if (ENVIRONMENT_IS_NODE && !globalThis.WebSocket) {
+              globalThis.WebSocket = /** @type{(typeof WebSocket)} */(require('ws'));
             }
-            ws = new WebSocketConstructor(url, opts);
+#endif // ENVIRONMENT_MAY_BE_NODE
+            ws = new WebSocket(url, opts);
             ws.binaryType = 'arraybuffer';
           } catch (e) {
 #if SOCKET_DEBUG
@@ -515,10 +511,12 @@ addToLibrary({
         sock.connecting = true;
       },
       listen(sock, backlog) {
+#if !ENVIRONMENT_MAY_BE_NODE
+        throw new FS.ErrnoError({{{ cDefs.EOPNOTSUPP }}});
+#else
         if (!ENVIRONMENT_IS_NODE) {
           throw new FS.ErrnoError({{{ cDefs.EOPNOTSUPP }}});
         }
-#if ENVIRONMENT_MAY_BE_NODE
         if (sock.server) {
            throw new FS.ErrnoError({{{ cDefs.EINVAL }}});  // already listening
         }

test/codesize/test_codesize_hello_dylink_all.json

@@ -1,7 +1,7 @@
 {
-  "a.out.js": 244343,
+  "a.out.js": 244388,
   "a.out.nodebug.wasm": 577478,
-  "total": 821821,
+  "total": 821866,
   "sent": [
     "IMG_Init",
     "IMG_Load",