Fix misleading guidance on disallowed host

[itowlson]

If you make a HTTP request to a disallowed host, Spin currently recommends that you add https://whatever:{80|443} (default port for your scheme) to your AOH. E.g.

// Rust
spin_sdk::http::send(Request::get("http://localhost:23234"))

// Message
To allow requests, add 'allowed_outbound_hosts = ["https://localhost:80"]' to the manifest component section.

This PR displays the original scheme of the request, and the custom port if one was used:

To allow requests, add 'allowed_outbound_hosts = ["http://localhost:23234"]' to the manifest component section.

Apologies for the lack of tests. The function is a bit monolithic at the moment; after release, we can look into factoring out more testable bits such as the validation/error routine.

[rylev]

Nit:

Suggested change

	let port = match port {
	Some(port_str) => port_str.to_string(),
	None => uri
	.scheme()
	.and_then(|s| (s == &Scheme::HTTP).then_some(80))
	.unwrap_or(443)
	.to_string(),
	};
	let port = port.unwrap_or_else(|| uri
	.scheme()
	.and_then(|s| (s == &Scheme::HTTP).then_some("80"))
	.unwrap_or("443"))