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/services/ngalert/api/tooling/cmd/clean-swagger/main.go

@@ -3,8 +3,8 @@ package main
 import (
 	"encoding/json"
 	"flag"
-	"io/ioutil"
 	"log"
+	"os"
 	"strings"
 )
 
@@ -22,7 +22,7 @@ func main() {
 	}
 
 	//nolint
-	b, err := ioutil.ReadFile(input)
+	b, err := os.ReadFile(input)
 	if err != nil {
 		log.Fatal(err)
 	}
@@ -101,7 +101,7 @@ func main() {
 		log.Fatal(err)
 	}
 
-	err = ioutil.WriteFile(output, out, 0644)
+	err = os.WriteFile(output, out, 0644)
 	if err != nil {
 		log.Fatal(err)
 	}

pkg/services/ngalert/api/tooling/definitions/alertmanager_test.go

@@ -3,7 +3,7 @@ package definitions
 import (
 	"encoding/json"
 	"errors"
-	"io/ioutil"
+	"os"
 	"strings"
 	"testing"
 
@@ -808,10 +808,10 @@ alertmanager_config: |
 func Test_GettableUserConfigRoundtrip(t *testing.T) {
 	// raw contains secret fields. We'll unmarshal, re-marshal, and ensure
 	// the fields are not redacted.
-	yamlEncoded, err := ioutil.ReadFile("alertmanager_test_artifact.yaml")
+	yamlEncoded, err := os.ReadFile("alertmanager_test_artifact.yaml")
 	require.Nil(t, err)
 
-	jsonEncoded, err := ioutil.ReadFile("alertmanager_test_artifact.json")
+	jsonEncoded, err := os.ReadFile("alertmanager_test_artifact.json")
 	require.Nil(t, err)
 
 	// test GettableUserConfig (yamlDecode -> jsonEncode)
@@ -1031,7 +1031,7 @@ routes:
 }
 
 func Test_Marshaling_Validation(t *testing.T) {
-	jsonEncoded, err := ioutil.ReadFile("alertmanager_test_artifact.json")
+	jsonEncoded, err := os.ReadFile("alertmanager_test_artifact.json")
 	require.Nil(t, err)
 
 	var tmp GettableUserConfig