[CI Minutes] Re-expose CI plan minutes data through GraphQL in GL.com

Re-expose CI plan minutes data through GraphQL in GL.com.

For this to work, we can load the schemas in both CustomerDot and GL.com: https://www.graphql-tools.com/docs/remote-schemas/. @shreyasagarwal is looking into this.

We would be using the Gitlab::SubscriptionPortal::Client.plans_data service call in a resolver. This branch is used as an exploration of this work: https://gitlab.com/gitlab-org/gitlab/-/merge_requests/new?merge_request%5Bsource_branch%5D=323938-mlunoe-explore-re-exposing-customer-dot-graphql

See the CustomerDot BE ticket here: customers-gitlab-com#2628 (comment 506935713)