all: Remove usage of deprecated io/ioutil (#7971)

As of Go 1.16 io/ioutil is deprecated. This replaces usage with the
corresponding functions in package os and package io.

lib/osutil/atomic_unix_test.go

@@ -12,7 +12,6 @@
 package osutil
 
 import (
-	"io/ioutil"
 	"os"
 	"syscall"
 	"testing"
@@ -24,7 +23,7 @@ func TestTempFilePermissions(t *testing.T) {
 	oldMask := syscall.Umask(0)
 	defer syscall.Umask(oldMask)
 
-	fd, err := ioutil.TempFile("", "test")
+	fd, err := os.CreateTemp("", "test")
 	if err != nil {
 		t.Fatal(err)
 	}