Maintenance: refactor servers updater code

- Require at least 80% of number of servers now to pass
- Each provider is in its own package with a common structure
- Unzip package with unzipper interface
- Openvpn package with extraction and download functions

internal/updater/providers/fastestvpn/sort.go

@@ -0,0 +1,16 @@
+package fastestvpn
+
+import (
+	"sort"
+
+	"github.com/qdm12/gluetun/internal/models"
+)
+
+func sortServers(servers []models.FastestvpnServer) {
+	sort.Slice(servers, func(i, j int) bool {
+		if servers[i].Country == servers[j].Country {
+			return servers[i].Hostname < servers[j].Hostname
+		}
+		return servers[i].Country < servers[j].Country
+	})
+}