Migrate OrderSummary component to GraphQL

What does this MR do?

This MR is just about porting the existing component OrderSummary from Vuex to GraphQL. Our goal is to re-create the current purchase flow with GraphQL instead of Vuex.

So, despite this MR is a little bit big it does just two things:

• Prepares the init step that the app uses to render the OrderSummary component.
• Ports the SubscriptionDetails component to GraphQL so treat this MR as an MR that changes the backend of Vue.js components from Vuex to Apollo.

Additional notes:

• Yes, the code may be ugly in some places but this is the 1st MR out of the 4 or 5.
• All non-blocking suggestions will be addressed in the next MRs.

See this epic for more information.

Related: #321648 (closed)

How to test it?

Enable the corresponding feature flag: Feature.enable(:new_route_ci_minutes_purchase).

Screenshots (strongly suggested)

Not applicable. Everything stayed the same.

Does this MR meet the acceptance criteria?

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