ledc: Move ledc unit test to test_apps pytest framework

Add ledc_hal_set_duty_start and ledc_hal_set_duty_int_part to IRAM
Fix test_ledc.c minor issues

components/driver/test_apps/ledc/pytest_ledc.py

@@ -0,0 +1,19 @@
+# SPDX-FileCopyrightText: 2021-2022 Espressif Systems (Shanghai) CO LTD
+# SPDX-License-Identifier: CC0-1.0
+
+import pytest
+from pytest_embedded_idf import IdfDut
+
+
+@pytest.mark.supported_targets
+@pytest.mark.generic
+@pytest.mark.parametrize(
+    'config',
+    [
+        'iram_safe',
+        'release',
+    ],
+    indirect=True,
+)
+def test_ledc(dut: IdfDut) -> None:
+    dut.run_all_single_board_cases()