Maint: hardcoded data in JSON embedded file

- Server information, versions and timestamps together in internal/constants/servers.json
- breaking change: updater cli uses -enduser instead of -file
- breaking change: updater cli uses -maintainer instead of -stdout
- Fix: replace special last a character with 'a' from Bogota for PrivateVPN
- Feat: do not write out servers and timestamp if no change was detected

.golangci.yml

@@ -17,6 +17,9 @@ issues:
     - path: internal/configuration/
       linters:
         - dupl
+    - path: internal/constants/
+      linters:
+        - dupl
     - text: "exported: exported var Err*"
       linters:
         - revive