freertos: Add blank freertos test app

This commit adds a blank FreeRTOS test app in preparation for migrating of
FreeRTOS unit tests to the created test app.

components/freertos/test_apps/freertos/pytest_freertos.py

@@ -0,0 +1,13 @@
+# SPDX-FileCopyrightText: 2022 Espressif Systems (Shanghai) CO LTD
+# SPDX-License-Identifier: Apache-2.0
+
+import pytest
+from pytest_embedded import Dut
+
+
+@pytest.mark.supported_targets
+@pytest.mark.generic
+def test_freertos(dut: Dut) -> None:
+    dut.expect_exact('Press ENTER to see the list of tests')
+    dut.write('*')
+    dut.expect_unity_test_output()