repl: hide editor mode if not used in a terminal

The editor mode is only useable when used as terminal. Hide it from
the user in case the repl terminal option is not set.

PR-URL: https://github.com/nodejs/node/pull/26240
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Anto Aravinth <anto.aravinth.cse@gmail.com>
Reviewed-By: Roman Reiss <me@silverwind.io>
Reviewed-By: Jeremiah Senkpiel <fishrock123@rocketmail.com>

lib/repl.js

@@ -1479,16 +1479,16 @@ function defineDefaultCommands(repl) {
       this.displayPrompt();
     }
   });
-
+  if (repl.terminal) {
     repl.defineCommand('editor', {
       help: 'Enter editor mode',
       action() {
-      if (!this.terminal) return;
         _turnOnEditorMode(this);
         this.outputStream.write(
           '// Entering editor mode (^D to finish, ^C to cancel)\n');
       }
     });
+  }
 }
 
 function regexpEscape(s) {

test/parallel/test-repl-save-load.js

@@ -61,7 +61,7 @@ assert.strictEqual(fs.readFileSync(saveFileName, 'utf8'),
     '}'
   ];
   const putIn = new ArrayStream();
-  const replServer = repl.start('', putIn);
+  const replServer = repl.start({ terminal: true, stream: putIn });
 
   putIn.run(['.editor']);
   putIn.run(cmds);

test/parallel/test-repl.js

@@ -439,7 +439,6 @@ const errorTests = [
     expect: [
       /\.break/,
       /\.clear/,
-      /\.editor/,
       /\.exit/,
       /\.help/,
       /\.load/,