Maint: rename utility names to be Openvpn specific

- GetTargetIPConnection to GetTargetIPOpenVPNConnection
- PickRandomConnection to PickRandomOpenVPNConnection

internal/provider/utils/pick.go

@@ -6,7 +6,7 @@ import (
 	"github.com/qdm12/gluetun/internal/models"
 )
 
-func PickRandomConnection(connections []models.OpenVPNConnection,
+func PickRandomOpenVPNConnection(connections []models.OpenVPNConnection,
 	source rand.Source) models.OpenVPNConnection {
 	return connections[rand.New(source).Intn(len(connections))] //nolint:gosec
 }