Use rest and spread operators in multi-threaded code. NFC

These operators are available everywhere that we can run mutli-threaded
code.

Author: sbc100

src/library.js

@@ -2911,7 +2911,7 @@ addToLibrary({
       // code paths as similar as possible on both sides.)
       // -1 - code is the encoding of a proxied EM_ASM, as a negative number
       // (positive numbers are non-EM_ASM calls).
-      return proxyToMainThread.apply(null, [-1 - code, sync].concat(args));
+      return proxyToMainThread(-1 - code, sync, ...args);
     }
 #endif
 #if ASSERTIONS

src/library_pthread.js

@@ -957,8 +957,8 @@ var LibraryPThread = {
 #if MEMORY64
   // Calls proxyToMainThread but returns a bigint rather than a number
   $proxyToMainThreadPtr__deps: ['$proxyToMainThread'],
-  $proxyToMainThreadPtr: function() {
-    return BigInt(proxyToMainThread.apply(null, arguments));
+  $proxyToMainThreadPtr: (...args) {
+    return BigInt(proxyToMainThread(...args));
   },
 #endif