Add up/down arrows for nutrition edit screen

[github-throwaway]

Problem

Entering nutrition facts is a tedious process. Ideally it should be done via OCR but in the meantime we can make it easier.right now users need to excessively scroll to enter data.

Proposed solution

Let's allowing input field jumping via extra buttons. This would speed up the data entry. Similar to native iOS keyboard. We need extra buttons because the native option is not implemented in flutter (flutter/flutter#10372)

Additional context

Mockups

Part of

• 🎯 What can I work on ? #525