LibWeb: Make Web::URL::host_is_domain accept an AK::URL::Host

Which allows us to avoid serializing the host only to try and reparse it
again as either an IPv4 or IPv6 address.

Userland/Libraries/LibWeb/Fetch/Fetching/Fetching.cpp

@@ -256,7 +256,7 @@ WebIDL::ExceptionOr<Optional<JS::NonnullGCPtr<PendingResponse>>> main_fetch(JS::
         // - request’s current URL’s scheme is "http"
         request->current_url().scheme() == "http"sv
         // - request’s current URL’s host is a domain
-        && URL::host_is_domain(request->current_url().serialized_host().release_value_but_fixme_should_propagate_errors())
+        && URL::host_is_domain(request->current_url().host())
         // FIXME: - Matching request’s current URL’s host per Known HSTS Host Domain Name Matching results in either a
         //          superdomain match with an asserted includeSubDomains directive or a congruent match (with or without an
         //          asserted includeSubDomains directive) [HSTS]; or DNS resolution for the request finds a matching HTTPS RR

Userland/Libraries/LibWeb/URL/URL.cpp

@@ -482,12 +482,10 @@ HTML::Origin url_origin(AK::URL const& url)
 }
 
 // https://url.spec.whatwg.org/#concept-domain
-bool host_is_domain(StringView host)
+bool host_is_domain(AK::URL::Host const& host)
 {
     // A domain is a non-empty ASCII string that identifies a realm within a network.
-    return !host.is_empty()
-        && !IPv4Address::from_string(host).has_value()
-        && !IPv6Address::from_string(host).has_value();
+    return host.has<String>() && host.get<String>() != String {};
 }
 
 // https://url.spec.whatwg.org/#concept-url-parser

Userland/Libraries/LibWeb/URL/URL.h

@@ -75,7 +75,7 @@ private:
 };
 
 HTML::Origin url_origin(AK::URL const&);
-bool host_is_domain(StringView host);
+bool host_is_domain(AK::URL::Host const&);
 
 // https://url.spec.whatwg.org/#concept-url-parser
 AK::URL parse(StringView input, Optional<AK::URL> const& base_url = {});