Treat absolute URL reqs as setting the tunnel destination in themselves

Previously if you tunnelled to a proxy server, and then sent GET
http://example.com, we treated the proxy server address as your intended
final destionation. That's clearly not quite right - it's weird that you
would do this, but if you do, the final request is itself another tunnel
really and we should treat that as the final destination.

Author: pimterry

src/util/request-utils.ts

@@ -400,7 +400,7 @@ export function preprocessRequest(req: ExtendedRawRequest, options: {
         req.path = getPathFromAbsoluteUrl(req.url!);
         req.destination = getDestination(
             req.protocol,
-            req.socket[LastTunnelAddress] ?? getHostFromAbsoluteUrl(req.url!)
+            getHostFromAbsoluteUrl(req.url!) // We ignore LastTunnelAddress - this *is* a tunnel
         );
 
         const proxyAuthHeader = getHeaderValue(rawHeaders, 'proxy-authorization');