Make overriding cookie encode work as one would expect

[andokai]

The value passed into the override encode function has already been converted to JSON and base64 encoded. I would have assume if you're creating an override then the value passed into the function would be the raw value.

Looks like a PR to address it was raised for Remix here:

remix-run/remix#10055

If it was rewritten for React Router is there any path for getting it merged in? It would make working with external APIs significantly easier, and the behaviour just seems more correct.