WebContent+LibWeb+LibJS: Simplify injection of JS console globals

Instead of creating a new global object and proxying everything through
it, we now evaluate console inputs inside a `with` environment.

This seems to match the behavior of WebKit and Gecko in my basic
testing, and removes the ConsoleGlobalObject which has been a source of
confusion and invalid downcasts.

The globals now live in a class called ConsoleGlobalObjectExtensions
(renamed from ConsoleGlobalObject since it's no longer a global object).

To make this possible, I had to add a way to override the initial
lexical environment when calling JS::Interpreter::run(). This is plumbed
via Web::HTML::ClassicScript::run().

Userland/Services/WebContent/WebContentConsoleClient.h

@@ -35,9 +35,7 @@ private:
     }
 
     ConnectionFromClient& m_client;
-    WeakPtr<JS::Realm> m_realm;
-    JS::GCPtr<class ConsoleEnvironmentSettingsObject> m_console_settings;
-    JS::Handle<ConsoleGlobalObject> m_console_global_object;
+    JS::Handle<ConsoleGlobalEnvironmentExtensions> m_console_global_environment_extensions;
 
     void clear_output();
     void print_html(DeprecatedString const& line);