Replace deprecated ioutil with io and os (#20776)

* Replace ioutil with io and os

* Replace ioutil in utils/file.go

* Minor fix to tests and excluded files

Co-authored-by: Tim Scheuermann <tim.scheuermann@mattermost.com>
Co-authored-by: Mattermod <mattermod@users.noreply.github.com>

scripts/config_generator/main_test.go

@@ -5,7 +5,6 @@ package main
 
 import (
 	"encoding/json"
-	"io/ioutil"
 	"os"
 	"testing"
 
@@ -15,14 +14,14 @@ import (
 )
 
 func TestDefaultsGenerator(t *testing.T) {
-	tmpFile, err := ioutil.TempFile("", "tempconfig")
+	tmpFile, err := os.CreateTemp("", "tempconfig")
 	defer os.Remove(tmpFile.Name())
 	require.NoError(t, err)
 	require.NoError(t, generateDefaultConfig(tmpFile))
 	_ = tmpFile.Close()
 	var config model.Config
 
-	b, err := ioutil.ReadFile(tmpFile.Name())
+	b, err := os.ReadFile(tmpFile.Name())
 	require.NoError(t, err)
 	require.NoError(t, json.Unmarshal(b, &config))
 	require.Equal(t, *config.SqlSettings.AtRestEncryptKey, "")