[UX] Update subscription card with Ramp data and appropriate actions on Manage Subscriptions page

## Problem

In order to support the new Zuora Orders and Ramps objects, we need to rethink 1) how ramped subscriptions should be displayed for the customers in the UI; and 2) what actions should be available for the ramped subscriptions.

1. When a subscription with Ramps is created in Zuora, it does not currently display clearly on the Manage Purchases page. 
1. Due to the complex nature of a Ramp deal, [sales ops has requested](https://gitlab.com/gitlab-com/business-technology/enterprise-apps/intake/-/issues/505#note_809749301) that users cannot self-add seats or renew a ramp. They should instead be directed to sales.

For additional details about Ramps, [demos](https://gitlab.com/groups/gitlab-org/-/epics/8748#ramp-demos-in-zuora-and-sfdc) and [sample data](https://gitlab.com/groups/gitlab-org/-/epics/8748#sample-data), see the parent epic: https://gitlab.com/groups/gitlab-org/-/epics/8748+

## Proposal

### What we show to the customer

1. Display every ramp period on the subscription card, so that the customer is aware how many seats they have access to for the time period.
2. Hide all subscription action buttons (other than link subscription to SaaS group), and display a message that directs the customer to Sales for subscription changes ([sales ops' request](https://gitlab.com/gitlab-com/business-technology/enterprise-apps/intake/-/issues/505#note_809749301)).

### What the customer can do

The subscription will be view only. Customer will not be able to make changes to the subscription via Customer Portal.

## Design

This is a fairly complicated topic, and updating how we display information in the subscription card is a major part of this, so I've recorded 2 videos to walk through the context and the changes.

* [Part 1/2: Ramps overview and why we can't use the current subscription card to display ramps](https://www.loom.com/share/d7fb7744acd14815ae909a64afacf6a4) (4 mins)
* [Part 2/2: Overview of subscription card changes and how ramped subscriptions are shown in the subscription card](https://www.loom.com/share/8f48c533691c43a6ac6349f1c7d37a13) (7.5 mins)

Questions that are answered in the video:

* Why can't we use the existing subscription card for ramps display?
* How does Zuora structure ramps data?
* What is the new subscription card display that's being proposed?
* How are we iterating into a new subscription card display? What is the MVC?

As I mentioned in the video, ramps will be the MVC of the subscription card information hierarchy updates. We'll handle other use cases in later iterations, and I've opened up [an issue for that](https://gitlab.com/gitlab-org/customers-gitlab-com/-/issues/5317). In the design section of this issue, you'll only find ramps-related mockups, so if you're looking for mockups for other use cases they can be found in https://gitlab.com/gitlab-org/customers-gitlab-com/-/issues/5317.

### Mockups and design resources

- Designs for ramps can be found in the design section of this issue
- [Figma file](https://www.figma.com/file/U9JvYVy1Ls9IKrrPw1vt38/Subscription-management?node-id=239%3A13266&t=9Up9sTBj5T9nmA8m-1)

## Solution validation

See [solution validation issue](https://gitlab.com/gitlab-org/ux-research/-/issues/2259#what-did-we-learn) for insights and recommendations

Story points: 2.0