example: refactor deep sleep example to make codes more structured

examples/system/deep_sleep/main/deep_sleep_example.h

@@ -0,0 +1,33 @@
+/*
+ * SPDX-FileCopyrightText: 2023 Espressif Systems (Shanghai) CO LTD
+ *
+ * SPDX-License-Identifier: Unlicense OR CC0-1.0
+ */
+
+#pragma once
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+#include "sdkconfig.h"
+
+#if CONFIG_EXAMPLE_GPIO_WAKEUP
+void example_deep_sleep_register_gpio_wakeup(void);
+#endif
+
+#if CONFIG_EXAMPLE_EXT0_WAKEUP
+void example_deep_sleep_register_ext0_wakeup(void);
+#endif
+
+#if CONFIG_EXAMPLE_EXT1_WAKEUP
+void example_deep_sleep_register_ext1_wakeup(void);
+#endif
+
+#if CONFIG_EXAMPLE_TOUCH_WAKEUP
+void example_deep_sleep_register_touch_wakeup(void);
+#endif
+
+#ifdef __cplusplus
+}
+#endif