Add subscription banner to group/subgroup pages

What does this MR do?

The subscription banner will be displayed on group/subgroup pages, as well as project pages for subgroups.

The most significant change here is looking up to the root_ancestor when checking for a gitlab_subscription. The decorated_subscription as well as the subscription_message now check project first, and group second.

Finishes: gitlab-org/growth/product#1550 (closed)

Screenshots

Does this MR meet the acceptance criteria?

Conformity

• Changelog entry
• 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