chore: Replace deprecated io/ioutil functions with recommended alternatives (#9542)

# Which Problems Are Solved

- The `io/ioutil` package was deprecated in Go 1.16.  
  - Reference: https://go.dev/doc/go1.16#ioutil  

# How the Problems Are Solved

- Replaced deprecated functions with their recommended alternatives:  
  - `ioutil.ReadFile` → `os.ReadFile`  
  - `ioutil.ReadAll` → `io.ReadAll`  
  - `ioutil.NopCloser` → `io.NopCloser`

internal/id/sonyflake.go

@@ -5,7 +5,7 @@ import (
 	"errors"
 	"fmt"
 	"hash/fnv"
-	"io/ioutil"
+	"io"
 	"net"
 	"net/http"
 	"os"
@@ -200,7 +200,7 @@ func metadataWebhookID() (uint16, error) {
 	if resp.StatusCode >= 400 && resp.StatusCode < 600 {
 		return 0, fmt.Errorf("metadata endpoint returned an unsuccessful status code %d", resp.StatusCode)
 	}
-	body, err := ioutil.ReadAll(resp.Body)
+	body, err := io.ReadAll(resp.Body)
 	if err != nil {
 		return 0, err
 	}