src: add environment cleanup hooks

This adds pairs of methods to the `Environment` class and to public APIs
which can add and remove cleanup handlers.

Unlike `AtExit`, this API targets addon developers rather than
embedders, giving them (and Node’s internals) the ability to register
per-`Environment` cleanup work.

We may want to replace `AtExit` with this API at some point.

Many thanks for Stephen Belanger for reviewing the original version of
this commit in the Ayo.js project.

Refs: https://github.com/ayojs/ayo/pull/82
PR-URL: https://github.com/nodejs/node/pull/19377
Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>
Reviewed-By: James M Snell <jasnell@gmail.com>

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