AK+Everywhere: Change URL::path() to serialize_path()

This now defaults to serializing the path with percent decoded segments
(which is what all callers expect), but has an option not to. This fixes
`file://` URLs with spaces in their paths.

The name has been changed to serialize_path() path to make it more clear
that this method will generate a new string each call (except for the
cannot_be_a_base_url() case). A few callers have then been updated to
avoid repeatedly calling this function.

Userland/DevTools/SQLStudio/MainWidget.cpp

@@ -480,7 +480,7 @@ void MainWidget::drop_event(GUI::DropEvent& drop_event)
             if (!scheme.equals_ignoring_ascii_case("file"sv))
                 continue;
 
-            auto lexical_path = LexicalPath(url.path());
+            auto lexical_path = LexicalPath(url.serialize_path());
             open_script_from_file(lexical_path);
         }
     }