Add missing destroy function.

The component allocates resources (timers, event loop) in relay_chn_create but never frees them. This is a resource leak.
Hence, a destroy function added to free the resources gracefully.

Fixes #1048.

test_apps/main/test_relay_chn.c

@@ -27,9 +27,10 @@ void setUp(void) {
 }
 
 void tearDown(void) {
-    
+    relay_chn_destroy(); // Clean up after each test
 }
 
+
 // --- Basic Functionality Tests ---
 
 // TEST_CASE 1: Test that relay channels initialize correctly to RELAY_CHN_STATE_FREE