Parametrize addon purchase details component

What does this MR do and why?

We would like to reuse the components for showing purchase summary for CI Minutes and Storage

Related to #327891 (closed)

Screenshots or screen recordings

How to set up and validate locally

• Run rails c
• Run Feature.enable(:new_route_storage_purchase) to enable the feature flag for Storage flow
• Run Feature.enable(:new_route_ci_minutes_purchase) to enable the feature flag for CI Minutes flow

Storage flow

• Navigate to http://localhost:3000/-/subscriptions/buy_storage?selected_group=<id_of_an_existing_group>
• You should see an update component on the page

CI Minutes flow (unchanged, posting to avoid regressions)

• Navigate to http://localhost:3000/-/subscriptions/buy_minutes?selected_group=<id_of_an_existing_group> to verify it

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.