storage: stop using deprecated io/ioutil

This replaces deprecated ioutil variables and functions as follows:

* ioutil.ReadDir -> os.ReadDir
* ioutil.ReadFile -> os.ReadFile
* ioutil.TempDir -> os.MkdirTemp
* ioutil.TempFile -> os.CreateTemp
* ioutil.WriteFile -> os.WriteFile

The ReadDir conversion involves an API change, the replacement
function returns a slice of fs.DirEntry instead of fs.FileInfo.
Where appropriate, the surrounding code has been adjusted; mostly,
that means using DirEntry.Type() instead of FileInfo.Mode().
Applying this change to the IoUtil interface would mean changing its
API, so this is left for later.

Signed-off-by: Stephen Kitt <skitt@redhat.com>

pkg/volume/util/util_test.go

@@ -17,7 +17,6 @@ limitations under the License.
 package util
 
 import (
-	"io/ioutil"
 	"os"
 	"reflect"
 	"runtime"
@@ -93,7 +92,7 @@ spec:
 	}
 
 	for _, test := range tests {
-		tempFile, err := ioutil.TempFile("", "podfile")
+		tempFile, err := os.CreateTemp("", "podfile")
 		defer os.Remove(tempFile.Name())
 		if err != nil {
 			t.Fatalf("cannot create temporary file: %v", err)