fix(uart): enlarged task stack size for uart_async_rxtxtasks example

Meanwhile, added CI pytest for some UART examples

Closes https://github.com/espressif/esp-idf/issues/15363

examples/peripherals/uart/uart_async_rxtxtasks/pytest_async_rxtxtasks.py

@@ -0,0 +1,10 @@
+# SPDX-FileCopyrightText: 2025 Espressif Systems (Shanghai) CO LTD
+# SPDX-License-Identifier: CC0-1.0
+import pytest
+from pytest_embedded import Dut
+
+
+@pytest.mark.supported_targets
+@pytest.mark.generic
+def test_uart_async_rxtxtasks_example(dut: Dut) -> None:
+    dut.expect_exact('TX_TASK: Wrote 11 bytes')