Key error for countries with same dial code

[maddyb99]

Describe the bug
Multiple countries/areas with same dialogue can fail the drop-down on login screen since dial code is being used as a key

To Reproduce
Steps to reproduce the behavior:

1. Go to country_codes_constant.dart
2. Uncomment commented countries and reload.
3. Select one of the countries in dropdown
4. See error

Expected behavior
All countries and dial codes should be selectable

If someone can refactor the key and how the provider manages country of a user, it would be of great help!🙏