Add `Zuora Subscriptions` readonly Admin action

Problem

Some readonly admins often require / might benefit from having access to a readonly version of the Zuora Subscriptions action (Zuora Subscriptions tab when you click on a customer or billing account.).

Recently as part of a compliance update we removed the access to this tab for 400+ team members because these team members were moved to readonly and this actions is currently only available for Admin managers.

More optional context here - External

Proposal

• Update the zuora_subscriptions action so it is possible to render its associated view as readonly
• Allow the zuora_subscriptions action for readonly Admins

Approval for merging

@mgass1 Would you please ✅ this issue for approval? (A reaction to this comment should be enough)

I have referenced the external conversation for the MR reviewers reference but given this is a roles related change, want to make sure there is a formal "this is OK to to ship from the product perspective" for the maintainer merging this.