test: Migrate form trigger test from cypress -> playwright (#19453)

packages/testing/playwright/utils/index-helper.ts

@@ -0,0 +1,10 @@
+import type { Locator } from '@playwright/test';
+
+/**
+ * Returns a locator for a specific element by index, or the original locator if no index is provided.
+ * Without an index, Playwright throws an error when multiple matching elements are found.
+ * @see https://playwright.dev/docs/locators#strictness
+ */
+export function locatorByIndex(locator: Locator, index?: number) {
+	return typeof index === 'number' ? locator.nth(index) : locator;
+}