test: move heapdump tests to pummel

The heapdump tests take a lot more time to run than our other tests in
parallel. They are also a bit of an internal test that perhaps does not
need to be run on every commit on every platform. This change moves them
to the pummel directory where they will be run on a single platform once
a day in CI.

This shaves more than 20 seconds off `make test` on my laptop, FWIW.

PR-URL: https://github.com/nodejs/node/pull/25181


Reviewed-By: Joyee Cheung <joyeec9h3@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Matheus Marchini <mat@mmarchini.me>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>
Reviewed-By: James M Snell <jasnell@gmail.com>