refactor Nordigen and Category autocomplete usage (#784)

The final `Autocomplete` refactors. After this is merged what's
remaining is to do extensive testing and address the bugs in
https://github.com/actualbudget/actual/issues/773

This PR moves `Nordigen` autocomplete to the new one without using a
feature flag. IMO this is a safe change given the simple nature of the
Nordigen autocomplete component.