feat(protonvpn): feature filters (#2182)

- `SECURE_CORE_ONLY`
- `TOR_ONLY`
- `P2P_ONLY`

internal/provider/protonvpn/updater/api.go

@@ -23,6 +23,7 @@ type logicalServer struct {
 	Region      *string          `json:"Region"`
 	City        *string          `json:"City"`
 	Servers     []physicalServer `json:"Servers"`
+	Features    uint16           `json:"Features"`
 }
 
 type physicalServer struct {