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.

internal/cache/file.go

@@ -2,7 +2,6 @@ package cache
 
 import (
 	"io"
-	"io/ioutil"
 	"os"
 	"path/filepath"
 	"runtime"
@@ -106,7 +105,7 @@ func (c *Cache) Save(h restic.Handle, rd io.Reader) error {
 
 	// First save to a temporary location. This allows multiple concurrent
 	// restics to use a single cache dir.
-	f, err := ioutil.TempFile(dir, "tmp-")
+	f, err := os.CreateTemp(dir, "tmp-")
 	if err != nil {
 		return err
 	}