test: use fs rimraf to refresh tmpdir

Now that the functionality is built into core, use it to
refresh the test suite's tmpdir.

PR-URL: https://github.com/nodejs/node/pull/30569


Reviewed-By: Jiawen Geng <technicalcute@gmail.com>
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Rich Trott <rtrott@gmail.com>
Reviewed-By: Ben Coe <bencoe@gmail.com>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>