Init MetricsWatcher during app startup (#2378)

Signed-off-by: Igor Egorov <[email protected]>

Author: igor-egorov

core/application/impl/kagome_application_impl.cpp

@@ -93,6 +93,7 @@ namespace kagome::application {
     app_state_manager->atShutdown([watchdog] { watchdog->stop(); });
 
     {  // Metrics
+      injector_.injectMetricsWatcher();
       auto metrics_registry = metrics::createRegistry();
 
       constexpr auto startTimeMetricName = "kagome_process_start_time_seconds";