This commit adds support for process.on("exit") by appending a listener to
the unload event. Luckily, unload works pretty much the same as on("exit")
since it won't schedule any additional work in the even loop either.
This commit also solves an error in the Node implementation, since "process.argv"
didn't contained the main module route as it was supposed to.
The promise approach still required permissions to be specified
at initialisation, rather than at request.
Using a Proxy instance solves this permission issue.
The Proxy instance approach also eliminates the need for the
await. Achieving direct compatibility with Node.js.
/ref pr #6392
/ref commit d16337cc9c
