Add a country code field on registration page besides "Mobile No." field.

[garg3133]

Currently, we have a restriction on registration/profileedit forms due to which the "Mobile No." and similar fields only take 'number' input. This is problematic for our alumni who are living overseas because they can't prefix their contact number with the country code.

We also can't just change the type of contact number fields from number to text because this restriction is applicable at database-level as well.

So, we should add a new 'Country code' field beside the contact number fields, which can either take text input or show a list of all the countries with their respective country codes which user can select from.