Add constant for address type codes and & update strings with constants

[daniellemaxwell]

Scope of changes

Creates a constant for the address type enum sent to the backend and replaces strings with constants in the address form.

Type of change

• bug fix
• new feature
• documentation
• other (describe)

Acceptance criteria

Describe how reviewers can test this change to be sure that it works correctly. Add a checklist if possible

Author checklist

• I have manually tested the change and/or added automation in the form of unit tests or integration tests
• I have updated the dependencies list
• I have recompiled and included new protocol buffers to reflect changes I made
• I have added new test fixtures as needed to support added tests
• Check this box if a reviewer can merge this pull request after approval (leave it unchecked if you want to do it yourself)
• I have moved the associated Shortcut story to "Ready for Review"

Reviewer(s) checklist

• Any new user-facing content that has been added for this PR has been QA'ed to ensure correct grammar, spelling, and understandability.

[pdamodaran]

LGTM!