runtime: change io/ioutil to io/os packages

Change io/ioutil to io/os packages because io/ioutil package
is deprecated from 1.16:

Discard => io.Discard
NopCloser => io.NopCloser
ReadAll => io.ReadAll
ReadDir => os.ReadDir
ReadFile => os.ReadFile
TempDir => os.MkdirTemp
TempFile => os.CreateTemp
WriteFile => os.WriteFile

Details: https://go.dev/doc/go1.16#ioutil

Fixes: #3265

Signed-off-by: bin <bin@hyper.sh>

src/runtime/virtcontainers/pkg/cgroups/utils_test.go

@@ -6,7 +6,6 @@
 package cgroups
 
 import (
-	"io/ioutil"
 	"os"
 	"path/filepath"
 	"strings"
@@ -110,7 +109,7 @@ func TestValidCgroupPath(t *testing.T) {
 func TestDeviceToCgroupDeviceRule(t *testing.T) {
 	assert := assert.New(t)
 
-	f, err := ioutil.TempFile("", "device")
+	f, err := os.CreateTemp("", "device")
 	assert.NoError(err)
 	f.Close()