vfs: address review comments

- Use getLazy utility for lazy loading VirtualFileSystem and SEAProvider
- Import getLazy from internal/util instead of manual ??= pattern

Author: mcollina

lib/internal/test_runner/mock/mock.js

@@ -34,6 +34,7 @@ const {
 } = require('internal/url');
 const {
   emitExperimentalWarning,
+  getLazy,
   getStructuredStack,
   kEmptyObject,
 } = require('internal/util');
@@ -53,7 +54,9 @@ const { _load, _nodeModulePaths, _resolveFilename, isBuiltin } = Module;
 const { join } = require('path');
 
 // Lazy-load VirtualFileSystem to avoid loading VFS code if fs mocking is not used
-let VirtualFileSystem;
+const lazyVirtualFileSystem = getLazy(
+  () => require('internal/vfs/virtual_fs').VirtualFileSystem,
+);
 function kDefaultFunction() {}
 const enableModuleMocking = getOptionValue('--experimental-test-module-mocks');
 const kSupportedFormats = [
@@ -809,7 +812,7 @@ class MockTracker {
       validateObject(files, 'options.files');
     }
 
-    VirtualFileSystem ??= require('internal/vfs/virtual_fs').VirtualFileSystem;
+    const VirtualFileSystem = lazyVirtualFileSystem();
     const vfs = new VirtualFileSystem({ __proto__: null, moduleHooks: true });
 
     // Add initial files if provided

lib/internal/vfs/sea.js

@@ -1,14 +1,18 @@
 'use strict';
 
 const { isSea } = internalBinding('sea');
-const { kEmptyObject } = require('internal/util');
+const { kEmptyObject, getLazy } = require('internal/util');
 
 // Lazy-loaded VFS
 let cachedSeaVfs = null;
 
 // Lazy-load VirtualFileSystem and SEAProvider to avoid loading VFS code if not needed
-let VirtualFileSystem;
-let SEAProvider;
+const lazyVirtualFileSystem = getLazy(
+  () => require('internal/vfs/file_system').VirtualFileSystem,
+);
+const lazySEAProvider = getLazy(
+  () => require('internal/vfs/providers/sea').SEAProvider,
+);
 
 /**
  * Creates a VirtualFileSystem populated with SEA assets using the new Provider architecture.
@@ -23,8 +27,8 @@ function createSeaVfs(options = kEmptyObject) {
     return null;
   }
 
-  VirtualFileSystem ??= require('internal/vfs/file_system').VirtualFileSystem;
-  SEAProvider ??= require('internal/vfs/providers/sea').SEAProvider;
+  const VirtualFileSystem = lazyVirtualFileSystem();
+  const SEAProvider = lazySEAProvider();
 
   const prefix = options.prefix ?? '/sea';
   const moduleHooks = options.moduleHooks !== false;