src: flush V8 interrupts from Environment dtor

This avoids an edge-case memory leak.

Refs: https://github.com/nodejs/node/pull/32523#discussion_r399554491

PR-URL: https://github.com/nodejs/node/pull/32523


Reviewed-By: Matheus Marchini <mat@mmarchini.me>
Reviewed-By: James M Snell <jasnell@gmail.com>