refactor: move from io/ioutil to io and os package

The io/ioutil package has been deprecated as of Go 1.16, see
https://golang.org/doc/go1.16#ioutil. This commit replaces the existing
io/ioutil functions with their new definitions in io and os packages.

Signed-off-by: Eng Zer Jun <engzerjun@gmail.com>

snapshots/devmapper/snapshotter_test.go

@@ -23,7 +23,6 @@ import (
 	"context"
 	_ "crypto/sha256"
 	"fmt"
-	"io/ioutil"
 	"os"
 	"testing"
 	"time"
@@ -87,7 +86,7 @@ func TestSnapshotterSuite(t *testing.T) {
 	ctx = namespaces.WithNamespace(ctx, "testsuite")
 
 	t.Run("DevMapperUsage", func(t *testing.T) {
-		tempDir, err := ioutil.TempDir("", "snapshot-suite-usage")
+		tempDir, err := os.MkdirTemp("", "snapshot-suite-usage")
 		assert.NilError(t, err)
 		defer os.RemoveAll(tempDir)