refactor: simplify configuration handling for CMS URL

- Removed CmsServerBaseUrl utility class and updated references to directly access GwUrl from configuration.
- Adjusted frontoffice-deployment.yaml to remove CmsInternalBaseUrl environment variable.
- Updated appsettings for staging and main environments to reflect the correct CMS service URLs.
- Ensured consistent handling of GwUrl in TokenNotificationService and AddGrpcServices methods.

src/FrontOffice.Main/appsettings.Staging.json

@@ -1,5 +1,5 @@
 {
-  "GwUrl": "https://cms.se.kbs1.ir",
+  "GwUrl": "http://cms-svc:8080",
   "DownloadUrl": "",
   "EncryptionSettings": {
     "Key": "kmcQ3XTmH4mrdh8VHziuscyf8LLYjG//Kyni81nH/0E=",