[New CDot Nav] Migrate Zuora Contact Form to use GraphQL

Problem

Currently, the zuora_contact_form.vue updates contacts using the REST API and a page refresh to display the errors. This is not a great experience for the user.

Proposed solution

Update the zuora_contact_form.vue to use the GraphQL endpoint instead. This should also include error alerts and toasts as per the design: https://www.figma.com/file/iCqd9J7DOCTS7Q3CDcKdPX/Navigation-for-CDot-to-represent-User%2FBillingAccount-data-structure?node-id=675%3A55086&mode=dev.

See Handle errors from updating billing contacts (#7793) for specifics on error handling.