Browser+LibWeb+WebContent: Allow Browser to load local files

To achieve this goal:
 - The Browser unveils "/tmp/portal/filesystemaccess"
 - Pass the page through LoadRequest => ResourceLoader
 - ResourceLoader requests a file to the FileSystemAccessServer via IPC
 - OutOfProcessWebView handles it and sends a file descriptor back to
 the Page.

Userland/Libraries/LibWeb/Loader/LoadRequest.cpp

@@ -19,6 +19,7 @@ LoadRequest LoadRequest::create_for_url_on_page(const AK::URL& url, Page* page)
         String cookie = page->client().page_did_request_cookie(url, Cookie::Source::Http);
         if (!cookie.is_empty())
             request.set_header("Cookie", cookie);
+        request.set_page(*page);
     }
 
     return request;