Refactor to remove redundant initialization and add NVS storage tests

- Removed unnecessary calls to relay_chn_create and g_is_component_initialized in multiple test cases across test_relay_chn_core_single.c, test_relay_chn_listener_multi.c, and test_relay_chn_listener_single.c.
- Introduced new test files for NVS functionality: test_relay_chn_nvs_multi.c and test_relay_chn_nvs_single.c, covering initialization, direction setting, invalid parameters, and erase operations.
- Updated partition table configuration to support NVS storage, including the addition of a new partition file part_nvs.csv.
- Adjusted sdkconfig files to enable NVS support and configure custom partition settings for relay channels.

test_apps/main/test_common.h

@@ -21,3 +21,6 @@ extern const uint32_t test_delay_margin_ms;
 
 // Init state
 extern bool g_is_component_initialized;
+
+// Reset channels to Idle state
+void reset_channels_to_idle_state(void);