test: forbid `common.mustCall*()` in process exit handlers

`common.mustCall()` and `common.mustCallAtLeast()` need to be called
before process exit handlers to work because checks are done inside a
process exit handler. Detect if being used inside a process exit handler
and throw.

PR-URL: https://github.com/nodejs/node/pull/17453


Reviewed-By: Anatoli Papirovski <apapirovski@mac.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Khaidi Chu <i@2333.moe>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>