Cleanup and replace constants

- Delete unused declaration of `g_is_component_initialized`.
- Replace the following constants with approprite config options:
  + `relay_chn_count` > `CONFIG_RELAY_CHN_COUNT`
  + `opposite_inerta_ms` > `CONFIG_RELAY_CHN_OPPOSITE_INERTIA_MS`
- Replace the definition of the `test_delay_margin_ms` constant with  `#define TEST_DELAY_MARGIN_MS 50` for preprocessor calculations.

test_apps/main/test_common.h

@@ -13,14 +13,9 @@ extern const char *TEST_TAG;
 // GPIO configurations
 extern const uint8_t gpio_map[];
 extern const uint8_t gpio_count;
-extern const uint8_t relay_chn_count;
 
 // Config variables for tests
-extern const uint32_t opposite_inertia_ms;
-extern const uint32_t test_delay_margin_ms;
-
-// Init state
-extern bool g_is_component_initialized;
+#define TEST_DELAY_MARGIN_MS 50
 
 // Reset channels to Idle state
 void reset_channels_to_idle_state(void);