feat: Tomcat 스레드 메트릭 노출 활성화

- mbeanregistry.enabled: true 추가
- tomcat.threads.current/busy/config.max 메트릭 노출

Author: Jinyshin

src/main/resources/application-staging.yml

@@ -58,6 +58,8 @@ server:
   tomcat:
     max-threads: 200
     accept-count: 100
+    mbeanregistry:
+      enabled: true
 
 management:
   endpoints: