test: move inspector tests to parallel/sequential

* remove inspector directory artifacts

PR-URL: https://github.com/nodejs/node/pull/16197


Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Refael Ackermann <refack@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>