[Order Form] Use `TextInputAutocapitalization.characters` or UIKit equivalent to capitalize postcodes

[joshheald]

When editing or adding a customer address in the Order Form, it would be convenient for the user if the keyboard used capitals for all letters in the postcode, at least for some locales such as GB, CA, and more.

There may be a locale-aware postcode format mask available, which would be even better.

If this is to difficult to make work correctly for most locales in a reasonable time, it can be closed.

[dangermattic]

🚫 Please add a type label (e.g. type: enhancement) and a feature label (e.g. feature: stats) to this issue.