[client] make /var/lib/netbird paths configurable (#3084)

- NB_STATE_DIR
- NB_UNCLEAN_SHUTDOWN_RESOLV_FILE
- NB_DNS_STATE_FILE

client/internal/statemanager/path.go

@@ -1,23 +1,16 @@
 package statemanager
 
 import (
+	"github.com/netbirdio/netbird/client/configs"
 	"os"
 	"path/filepath"
-	"runtime"
 )
 
 // GetDefaultStatePath returns the path to the state file based on the operating system
 // It returns an empty string if the path cannot be determined.
 func GetDefaultStatePath() string {
-	switch runtime.GOOS {
-	case "windows":
-		return filepath.Join(os.Getenv("PROGRAMDATA"), "Netbird", "state.json")
-	case "darwin", "linux":
-		return "/var/lib/netbird/state.json"
-	case "freebsd", "openbsd", "netbsd", "dragonfly":
-		return "/var/db/netbird/state.json"
+	if path := os.Getenv("NB_DNS_STATE_FILE"); path != "" {
+		return path
 	}
-
-	return ""
-
+	return filepath.Join(configs.StateDir, "state.json")
 }