test: add integration tests for setting primary email and phone number

Add comprehensive test coverage for updating user primary contact details through the Clerk API, including:

- Test for changing the primary email address to a secondary email and restoring the original
- Test for changing the primary phone number to a secondary phone and restoring the original
- Mock API response fixtures for both email and phone update workflows
- Validation that primary identifier changes are properly reflected in the user object and client session

Author: deevus