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>