lib: only build the ESM facade for builtins when they are needed

We previously build the ESM facade for builtins even when they
are not directly import'ed (which rarely happens for internal
builtins as that requires --expose-internals). This patch removes
the eager generation to avoid the overhead and the extra
promises created in facade building when it's not reqested by the user.
When the facade is needed the ESM loader that can be requested
it in the translator on-demand.

Drive-by: set the ModuleWrap prototype to null in the built-in
snapshot.

Author: joyeecheung

lib/internal/bootstrap/realm.js

@@ -198,6 +198,9 @@ const {
   setInternalLoaders,
 } = internalBinding('builtins');
 
+const { ModuleWrap } = internalBinding('module_wrap');
+ObjectSetPrototypeOf(ModuleWrap.prototype, null);
+
 const getOwn = (target, property, receiver) => {
   return ObjectPrototypeHasOwnProperty(target, property) ?
     ReflectGet(target, property, receiver) :
@@ -338,16 +341,11 @@ class BuiltinModule {
       const internal = StringPrototypeStartsWith(this.id, 'internal/');
       this.exportKeys = internal ? [] : ObjectKeys(this.exports);
     }
-    this.getESMFacade();
-    this.syncExports();
     return this.exports;
   }
 
   getESMFacade() {
     if (this.module) return this.module;
-    const { ModuleWrap } = internalBinding('module_wrap');
-    // TODO(aduh95): move this to C++, alongside the initialization of the class.
-    ObjectSetPrototypeOf(ModuleWrap.prototype, null);
     const url = `node:${this.id}`;
     const builtin = this;
     const exportsKeys = ArrayPrototypeSlice(this.exportKeys);