Support REAPER option "Allow complete unload of VST plug-ins"

[helgoboss]

Right now it crashes when this is enabled which indicates a cleanup issue.

[helgoboss]

Ah, that problem just occurs if the new projection server is running.

[helgoboss]

The problem here is twofold:

1. hyper's graceful shutdown sequence can be blocked by open browser tabs.
   • The problem is that open browser tabs can still have an established TCP connection - even if keep-alive is disabled.
   • In my case this happened for example with Chrome on Windows.
   • Temporary solution: Patch hyper to force a connection close when shutting down.
   • Preferred solution: Make this way of shutting down an official option for hyper.
2. Tokio runtime using basic_scheduler() won't release the ports, even if warp/hyper have managed to shutdown properly.
   • This is a problem because once the ReaLearn plug-in is unloaded, we would expect it to just work if added again. But it won't. It will not be able to start the server because the port is still occupied.
   • Solution: Use threaded_scheduler() instead of basic_scheduler(). This fixes the issue and the ports get properly released!