util: fix wrong usage of Error.prepareStackTrace

The return value of Error.prepareStackTrace will become the result
of Error.stack accesses. Setting Error.stack inside this callback
relies on the fact that the magic get accessor detects the change in
the middle of formatting, and is unnecessary in this instance.

Refs: v8#96

PR-URL: #27250
Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>
Reviewed-By: Masashi Hirano <shisama07@gmail.com>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>
Reviewed-By: Gus Caplan <me@gus.host>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Anto Aravinth <anto.aravinth.cse@gmail.com>

lib/internal/util.js

@@ -347,7 +347,7 @@ function isInsideNodeModules() {
     // the perf implications should be okay.
     getStructuredStack = runInNewContext(`(function() {
       Error.prepareStackTrace = function(err, trace) {
-        err.stack = trace;
+        return trace;
       };
       Error.stackTraceLimit = Infinity;