Description of Change

Closes #21907.

In nodejs/node#26788 (v12.0.0), Node.js added a bootstrapper to CreateEnvironment, which would prepare the main thread for execution any time an embedder created a new environment. However, this caused an unfortunate doubling-up effect; Node.js also ran bootstrapping (called prepareMainThreadExecution) for all other execution paths (like the repl, the actual main module, eval, etc). This meant that we'd see weird stuff like

> process.emit('warning', new Error('warn'))
(node:55797) Error: warn
(node:55797) Error: warn

since both execution pathways (env and whatever the actual execution was) were being exercised. To fix this, we can just remove bootstrapping code from CreateEnvironment. This also saves us a bunch of workaround code on our end, like the unsafe env block we had to prevent strange behavior during debugger setup. An upstream PR is open for this against Node.js itself, linked at bottom.

cc @MarshallOfSound @zcbenz @nornagon

Checklist

• PR description included and stakeholders cc'd
• npm test passes
• PR title follows semantic commit guidelines
• PR release notes describe the change in a way relevant to app developers, and are capitalized, punctuated, and past tense.

Release Notes

Notes: Fixed an issue where some logging would double-print.