module: remove useCustomLoadersIfPresent flag

The flag is always true and can be determined by isLoaderWorker solely.

PR-URL: #48655
Backport-PR-URL: #51239
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>
Reviewed-By: Antoine du Hamel <duhamelantoine1995@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Joyee Cheung <joyeec9h3@gmail.com>

lib/internal/modules/esm/loader.js

@@ -524,15 +524,13 @@ let emittedLoaderFlagWarning = false;
  * A loader instance is used as the main entry point for loading ES modules. Currently, this is a singleton; there is
  * only one used for loading the main module and everything in its dependency graph, though separate instances of this
  * class might be instantiated as part of bootstrap for other purposes.
- * @param {boolean} useCustomLoadersIfPresent If the user has provided loaders via the --loader flag, use them.
  * @returns {ModuleLoader}
  */
-function createModuleLoader(useCustomLoadersIfPresent = true) {
+function createModuleLoader() {
   let customizations = null;
-  if (useCustomLoadersIfPresent &&
-      // Don't spawn a new worker if we're already in a worker thread created by instantiating CustomizedModuleLoader;
-      // doing so would cause an infinite loop.
-      !require('internal/modules/esm/utils').isLoaderWorker()) {
+  // Don't spawn a new worker if we're already in a worker thread created by instantiating CustomizedModuleLoader;
+  // doing so would cause an infinite loop.
+  if (!require('internal/modules/esm/utils').isLoaderWorker()) {
     const userLoaderPaths = getOptionValue('--experimental-loader');
     if (userLoaderPaths.length > 0) {
       if (!emittedLoaderFlagWarning) {

lib/internal/process/esm_loader.js

@@ -11,10 +11,10 @@ let esmLoader;
 
 module.exports = {
   get esmLoader() {
-    return esmLoader ??= createModuleLoader(true);
+    return esmLoader ??= createModuleLoader();
   },
   async loadESM(callback) {
-    esmLoader ??= createModuleLoader(true);
+    esmLoader ??= createModuleLoader();
     try {
       const userImports = getOptionValue('--import');
       if (userImports.length > 0) {