fs: refactor to use ES2020 syntax

PR-URL: #41903
Reviewed-By: Tobias Nießen <[email protected]>
Reviewed-By: Antoine du Hamel <[email protected]>

Author: xtx1130

lib/fs.js

@@ -2516,7 +2516,7 @@ function realpathSync(p, options) {
       }
       resolvedLink = pathModule.resolve(previous, linkTarget);
 
-      if (cache) cache.set(base, resolvedLink);
+      cache?.set(base, resolvedLink);
       if (!isWindows) seenLinks[id] = linkTarget;
     }
 
@@ -3041,8 +3041,7 @@ ObjectDefineProperties(fs, {
     configurable: true,
     enumerable: true,
     get() {
-      if (promises === null)
-        promises = require('internal/fs/promises').exports;
+      promises ??= require('internal/fs/promises').exports;
       return promises;
     }
   }