Add NVS support for relay channel config persistence

- Introduced NVS configuration options in Kconfig.
- Implemented NVS initialization and deinitialization in relay_chn_core.
- Added functions for storing and retrieving relay channel direction and tilt sensitivity in NVS.
- Updated relay_chn_tilt and relay_chn_output to utilize NVS for state management.
- Created relay_chn_nvs.c and relay_chn_nvs.h for NVS-related functionalities.

Closes #1074.

CMakeLists.txt

@@ -15,7 +15,12 @@ else()
     list(APPEND srcs "src/relay_chn_ctl_single.c")
 endif()
 
+if(CONFIG_RELAY_CHN_NVS)
+    list(APPEND srcs "src/relay_chn_nvs.c")
+endif()
+
+
 idf_component_register(SRCS ${srcs}
                        INCLUDE_DIRS ${include_dirs}
                        PRIV_INCLUDE_DIRS ${priv_include_dirs}
-                       REQUIRES driver esp_timer esp_event)
+                       REQUIRES driver esp_timer esp_event nvs_flash)