Migrate form param request for Zuora HPM to GraphQL resolver

Problem

We currently use a separate controller endpoint to fetch payment form parameters for the Zuora HPM.

More information in this MR that consolidates the requests: https://gitlab.com/gitlab-org/customers-gitlab-com/-/merge_requests/13059+.

Proposal

We should migrate this to GraphQL to align with the rest of the application and have better control over values returned.

Started a POC here: https://gitlab.com/gitlab-org/customers-gitlab-com/-/merge_requests/13088+.