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

internal/models/servers.go

@@ -1,7 +1,7 @@
 package models
 
 type AllServers struct {
-	Version      uint16              `json:"version"`
+	Version      uint16              `json:"version"` // used for migration of the top level scheme
 	Cyberghost   CyberghostServers   `json:"cyberghost"`
 	Fastestvpn   FastestvpnServers   `json:"fastestvpn"`
 	HideMyAss    HideMyAssServers    `json:"hidemyass"`