Subscription Details: integrate GraphQL

What does this MR do?

This MR is part of a series that addresses gitlab-org/gitlab#273028 in creating the Subscription Details View for <strong data-sourcepos="16:116-16:132">Opt-In online</strong> customers.

Description	MR
Table and Details components	!57717 (merged)
User Info Component	!57852 (merged)
License History Component	!58660 (merged)
Subscription-Breakdown Component (integrates all the previous)	!58760 (merged)
Integrate GraphQL to provide data	👈 you are here

To see the changes locally

1. GDK should have no previous license

2. Set $CUSTOMER_PORTAL_URL to point to https://customers.stg.gitlab.com (and gdk restart)

3. Use Rails console to run: ApplicationSetting.current.update(cloud_license_enabled: true)

4. Go to /admin/cloud_license

5. Use the following activation code: XGmkoPM5BKUsqqUWKpnRYSrY

Screenshots (strongly suggested)

This MR does not contain UI changes but here's a preview of how's gonna look like:

Activation Form	Subscription Details	Activation Flow	Table with older license
		Screen_Recording_2021-04-14_at_09.36.31

Notes

• all the buttons have been removed in light of this discussion here

• the table order is supposed to show the Legacy License before the new one. This might be due to the fact that the activation code we're using for tests is referring to a license that has an earlier start date. I will verify this with the BE.

• success and failing scenario for the activation code will be handled in an ad-hoc Issue (to be created)

Does this MR meet the acceptance criteria?

Conformity

• 📋 Does this MR need a changelog?
  • I have included a changelog entry.
  • I have not included a changelog entry because the feature is under Application settings and does not introduce UI chagnes.
• [-] Documentation (if required)
• Code review guidelines
• Merge request performance guidelines
• Style guides
• [-] Database guides
• Separation of EE specific content

Availability and Testing

• Review and add/update tests for this feature/bug. Consider all test levels. See the Test Planning Process.
• [-] Tested in all supported browsers
• [-] Informed Infrastructure department of a default or new setting change, if applicable per definition of done

Security

If this MR contains changes to processing or storing of credentials or tokens, authorization and authentication methods and other items described in the security review guidelines:

• [-] Label as security and @ mention @gitlab-com/gl-security/appsec
• [-] The MR includes necessary changes to maintain consistency between UI, API, email, or other methods
• [-] Security reports checked/validated by a reviewer from the AppSec team