Give - Recurring Donations 2.7.0

* New: Added a "Blank Slate" for the Subscribers screen when no subscriptions are yet created.
* New: Added additional filters for developers to determine who has access to the Sync tool.
* Fix: Resolved an issue with renewal emails not being sent properly due to an incorrect permission check preventing webhooks from triggering the email.

Fix: Added checks in place to ensure that when a subscription is cancelled or completed that multiple emails are not sent to the donor or admin incorrectly.
Fix: If using Stripe Checkout 2.0 then it does not support displaying an image within the checkout so we removed code that caused an issue with their API. The error returning from Stripe was "The Stripe Gateway returned an error while creating the Checkout Session" due to the image.
Fix: Clicking on the "Resend Receipt" option on a renewal would not send the correct email template. Now it sends the "Renewal Receipt Email" template.

* Fix: There was an issue with manually syncing a Stripe subscription that would bring in failed or on-hold payments as renewals incorrectly. This has been fixed so that only invoices marked as paid are brought into GiveWP as renewals.
* Fix: Resolved an invalid capability argument within the `give_subscriber` WP user role. This resolves issues with membership plugins unable to correctly use the role.
* Improvement: Optimized the subscription count query to reduce the number of database queries when viewing certain screens in WP-Admin.