Add a test for execution of event loop exception handler

Investigating https://github.com/pyscript/pyscript/issues/1366, I found that there was a bug in Pyodide v0.22.1 that got fixed in v0.23.0.

In v0.23.0, the code as follows:
```
pyodide.runPython(`
import asyncio

async def main():
raise Exception("hi")

asyncio.ensure_future(main())
None
`)
```
executes the event loop exception handler:
```
Task exception was never retrieved
future: :4> exception=Exception('hi')>
```
whereas in v0.22.1 nothing is printed. I am not sure what PR fixed this. It doesn't seem to be related to refcounts. Anyways we should add a test if there isn't one.