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/Libraries/LibJS/Interpreter.h

@@ -66,7 +66,7 @@ public:
 
     ~Interpreter() = default;
 
-    ThrowCompletionOr<Value> run(Script&);
+    ThrowCompletionOr<Value> run(Script&, JS::GCPtr<Environment> lexical_environment_override = {});
     ThrowCompletionOr<Value> run(SourceTextModule&);
 
     Realm& realm();