Fix CTRL_CLOSE, CTRL_LOGOFF and CTRL_SHUTDOWN on windows

[Finomnis]

Fixes #7039.

Motivation

According to https://learn.microsoft.com/en-us/windows/console/handlerroutine#remarks, the windows signals CTRL_CLOSE, CTRL_LOGOFF and CTRL_SHUTDOWN immediately kill the process upon being handled.

The intention is that the handler of those signals performs cleanup tasks, and once completed, it returns and the process is killed.

This behavior is sadly not really compatible with an async system that is based on signals.

Solution

There are multiple possible ways to solve this; the easiest one being to simply never return from the handler thread. This works because Rust calls ExitProcess after its main (to my knowledge). I tested it on a project of mine, and it seems to work indeed.