test: avoid flaky debugger restart waits

Replace stepCommand('restart') with command('restart') in restart-related tests to avoid timing out while waiting for break output.

This keeps the assertions intact while avoiding a fragile BREAK_MESSAGE wait path seen in macOS unusual-path CI runs.

Refs: #61762

Author: inoway46

test/parallel/test-debugger-restart-message.js

@@ -25,7 +25,9 @@ const startCLI = require('../common/debugger');
       assert.strictEqual(cli.output.match(listeningRegExp).length, 1);
 
       for (let i = 0; i < RESTARTS; i++) {
-        await cli.stepCommand('restart');
+        await cli.command('restart');
+        await cli.waitFor(/Debugger attached\./);
+        await cli.waitForPrompt();
         assert.strictEqual(cli.output.match(listeningRegExp).length, 1);
       }
     } finally {

test/parallel/test-debugger-run-after-quit-restart.js

@@ -57,7 +57,7 @@ const path = require('path');
         { filename: script, line: 2 },
       );
     })
-    .then(() => cli.stepCommand('restart'))
+    .then(() => cli.command('restart'))
     .then(() => cli.waitForInitialBreak())
     .then(() => {
       assert.deepStrictEqual(