Handle ioutil deprecations (#53526)

* replace ioutil.ReadFile -> os.ReadFile

* replace ioutil.ReadAll -> io.ReadAll

* replace ioutil.TempFile -> os.CreateTemp

* replace ioutil.NopCloser -> io.NopCloser

* replace ioutil.WriteFile -> os.WriteFile

* replace ioutil.TempDir -> os.MkdirTemp

* replace ioutil.Discard -> io.Discard

pkg/api/preferences_test.go

@@ -2,7 +2,7 @@ package api
 
 import (
 	"encoding/json"
-	"io/ioutil"
+	"io"
 	"net/http"
 	"strings"
 	"testing"
@@ -60,7 +60,7 @@ func TestAPIEndpoint_GetCurrentOrgPreferences_LegacyAccessControl(t *testing.T)
 		response := callAPI(sc.server, http.MethodGet, getOrgPreferencesURL, nil, t)
 		assert.Equal(t, http.StatusOK, response.Code)
 		var resp map[string]interface{}
-		b, err := ioutil.ReadAll(response.Body)
+		b, err := io.ReadAll(response.Body)
 		assert.NoError(t, err)
 		assert.NoError(t, json.Unmarshal(b, &resp))
 		assert.Equal(t, "home", resp["homeDashboardUID"])