Improve messages in case of system exit. This prints a better set of error messages in case someone calls `os._exit()` or in C code `exit()` is used.

Resolves #3486.

- [x] Add a [CHANGELOG](https://github.com/pyodide/pyodide/blob/main/docs/project/changelog.md) entry

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---
name: Code improvement
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labels:
assignees: ""
---

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