vm: properly support symbols on globals

A regression has been introduced in node 18.2.0, it lakes the following snippet fails while it used to work in the past:

```
const assert = require('assert');
const vm = require('vm');
const global = vm.runInContext('this', vm.createContext());
const totoSymbol = Symbol.for('toto');
Object.defineProperty(global, totoSymbol, {
  enumerable: true,
  writable: true,
  value: 4,
  configurable: true,
});
assert(Object.getOwnPropertySymbols(global).includes(totoSymbol));
```

The PR that introduced the regression is: nodejs#42963. So I basically attempted to start understanding what it changed to make it still fix the initial issue while not breaking the symbol related one.

Fixes: nodejs#45983

src/node_contextify.cc

@@ -530,7 +530,9 @@ void ContextifyContext::PropertySetterCallback(
     return;
 
   USE(ctx->sandbox()->Set(context, property, value));
-  args.GetReturnValue().Set(value);
+  if (is_function) {
+    args.GetReturnValue().Set(value);
+  }
 }
 
 // static

test/parallel/test-vm-global-symbol.js

@@ -0,0 +1,14 @@
+'use strict';
+const assert = require('assert');
+const vm = require('vm');
+
+const global = vm.runInContext('this', vm.createContext());
+const totoSymbol = Symbol.for('toto');
+Object.defineProperty(global, totoSymbol, {
+  enumerable: true,
+  writable: true,
+  value: 4,
+  configurable: true,
+});
+assert(global[totoSymbol] === 4);
+assert(Object.getOwnPropertySymbols(global).includes(totoSymbol));