Dynamically removable HTTP routes and SNI domains

Together with the SNI improvements from v20.18.0 you can now add/remove HTTP routes dynamically, both for the root ("catch all") domain, and for any specific SNI domain.

If you added a route with

app.get("/hello", [](auto *res, auto *req) {

});

You now remove it with app.get("/hello", nullptr);

The same applies to routes added under a SNI name - browsing to the domain with app.domain("server_name") you can then remove the route added.

Note that you cannot remove WebSocket routes just yet (but doing so could make sense semantically).