test: move tmpdir to submodule of common

Move tmpdir functionality to its own module (common/tmpdir).

PR-URL: https://github.com/nodejs/node/pull/17856
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Gibson Fahnestock <gibfahn@gmail.com>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>
Reviewed-By: Joyee Cheung <joyeec9h3@gmail.com>

test/parallel/test-https-unix-socket-self-signed.js

@@ -4,7 +4,8 @@ const common = require('../common');
 if (!common.hasCrypto)
   common.skip('missing crypto');
 
-common.refreshTmpDir();
+const tmpdir = require('../common/tmpdir');
+tmpdir.refresh();
 
 const fixtures = require('../common/fixtures');
 const https = require('https');