Use node prefix for build-in modules (#3340)

It is basically a cosmetic thing, but has the following advantages:

1. Consistency with the official node documentation. The prefix is used
there.
2. It is easier to recognize the build-in modules.

tests/unit/global_vars/defaults_modules_spec.js

@@ -1,5 +1,5 @@
-const fs = require("fs");
-const path = require("path");
+const fs = require("node:fs");
+const path = require("node:path");
 
 const root_path = path.join(__dirname, "../../..");