Replace most usages of ioutil with the underlying function

The ioutil functions are deprecated since Go 1.17 and only wrap another
library function. Thus directly call the underlying function.

This commit only mechanically replaces the function calls.

cmd/restic/cmd_check.go

@@ -2,8 +2,8 @@ package main
 
 import (
 	"context"
-	"io/ioutil"
 	"math/rand"
+	"os"
 	"strconv"
 	"strings"
 	"sync"
@@ -171,7 +171,7 @@ func prepareCheckCache(opts CheckOptions, gopts *GlobalOptions) (cleanup func())
 	}
 
 	// use a cache in a temporary directory
-	tempdir, err := ioutil.TempDir(cachedir, "restic-check-cache-")
+	tempdir, err := os.MkdirTemp(cachedir, "restic-check-cache-")
 	if err != nil {
 		// if an error occurs, don't use any cache
 		Warnf("unable to create temporary directory for cache during check, disabling cache: %v\n", err)