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/metadata_test.go

@@ -21,7 +21,6 @@ package devmapper
 
 import (
 	"context"
-	"io/ioutil"
 	"os"
 	"path/filepath"
 	"strconv"
@@ -233,7 +232,7 @@ func TestPoolMetadata_GetDeviceNames(t *testing.T) {
 }
 
 func createStore(t *testing.T) (tempDir string, store *PoolMetadata) {
-	tempDir, err := ioutil.TempDir("", "pool-metadata-")
+	tempDir, err := os.MkdirTemp("", "pool-metadata-")
 	assert.NilError(t, err, "couldn't create temp directory for metadata tests")
 
 	path := filepath.Join(tempDir, "test.db")