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/tsdb/testdatasource/resource_handler.go

@@ -4,7 +4,6 @@ import (
 	"encoding/json"
 	"fmt"
 	"io"
-	"io/ioutil"
 	"net/http"
 	"sort"
 	"strconv"
@@ -118,7 +117,7 @@ func createJSONHandler(logger log.Logger) http.Handler {
 					logger.Warn("Failed to close response body", "err", err)
 				}
 			}()
-			b, err := ioutil.ReadAll(req.Body)
+			b, err := io.ReadAll(req.Body)
 			if err != nil {
 				logger.Error("Failed to read request body to bytes", "error", err)
 			} else {