New PIA servers support (#227)

* Adapt storage: SyncServers write to file option, export FlushToFile
* CLI built-in updater for old and new PIA servers
* Update hardcoded IP addresses for PIA old and new servers
* Add PIA old to allServers struct and update timestamps
* Adapt code to work with new and old PIA servers
* Remove PIA subdomains (unneeded) from resolver tool

internal/params/pia.go

@@ -10,6 +10,7 @@ import (
 
 // GetPortForwarding obtains if port forwarding on the VPN provider server
 // side is enabled or not from the environment variable PORT_FORWARDING
+// Only valid for older PIA servers for now
 func (r *reader) GetPortForwarding() (activated bool, err error) {
 	s, err := r.envParams.GetEnv("PORT_FORWARDING", libparams.Default("off"))
 	if err != nil {
@@ -61,3 +62,10 @@ func (r *reader) GetPIARegion() (region string, err error) {
 	choices := append(constants.PIAGeoChoices(), "")
 	return r.envParams.GetValueIfInside("REGION", choices)
 }
+
+// GetPIAOldRegion obtains the region for the PIA server from the
+// environment variable REGION
+func (r *reader) GetPIAOldRegion() (region string, err error) {
+	choices := append(constants.PIAOldGeoChoices(), "")
+	return r.envParams.GetValueIfInside("REGION", choices)
+}