module: enable dynamic import flag for esmodules

currently if you want to use dynamic import you must use both the
`--experimental-modules` and the `--harmony-dynamic-imports` flags.
Chrome is currently shipping dynamic import unflagged, the flag
only remains in V8 to guard embedders who have not set the appropriate
callback from throwing an unhandled rejection when the feature is used.

As such it is reasonable to enable the flag by default for
`--experimental-modules`

Backport-PR-URL: #17823
PR-URL: #18387
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Jan Krems <jan.krems@gmail.com>
Reviewed-By: Bradley Farias <bradley.meck@gmail.com>
Reviewed-By: Guy Bedford <guybedford@gmail.com>
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Tiancheng "Timothy" Gu <timothygu99@gmail.com>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Michaël Zasso <targos@protonmail.com>

doc/api/esm.md

@@ -33,8 +33,8 @@ node --experimental-modules my-app.mjs
 ### Supported
 
 Only the CLI argument for the main entry point to the program can be an entry
-point into an ESM graph. In the future `import()` can be used to create entry
-points into ESM graphs at run time.
+point into an ESM graph. Dynamic import can also be used to create entry points
+into ESM graphs at runtime.
 
 ### Unsupported
 

src/node.cc

@@ -4077,6 +4077,8 @@ static void ParseArgs(int* argc,
       config_preserve_symlinks = true;
     } else if (strcmp(arg, "--experimental-modules") == 0) {
       config_experimental_modules = true;
+      new_v8_argv[new_v8_argc] = "--harmony-dynamic-import";
+      new_v8_argc += 1;
     }  else if (strcmp(arg, "--loader") == 0) {
       const char* module = argv[index + 1];
       if (!config_experimental_modules) {

test/es-module/test-esm-dynamic-import.js

@@ -1,4 +1,4 @@
-// Flags: --experimental-modules --harmony-dynamic-import
+// Flags: --experimental-modules
 'use strict';
 const common = require('../common');
 const assert = require('assert');