node_runtime: Improve proxy mapping (#41807)

Closes #ISSUE

More accurately map localhost to `127.0.0.1`. Previously we would
lowercase and simply replace all instances of localhost inside of the
URL string, meaning query parameters, username, password etc. could not
contain the string `localhost` or contain uppercase letters without
getting modified. Added a test ensuring the mapping logic works. The
previous implementation would fail this new test.

Release Notes:

- Improved the behavior of mapping `localhost` to `127.0.0.1` when
passing configured proxy urls to `node`

crates/http_client/src/http_client.rs

@@ -16,7 +16,7 @@ use parking_lot::Mutex;
 #[cfg(feature = "test-support")]
 use std::fmt;
 use std::{any::type_name, sync::Arc};
-pub use url::Url;
+pub use url::{Host, Url};
 
 #[derive(Default, Debug, Clone, PartialEq, Eq, Hash)]
 pub enum RedirectPolicy {