Implement doCancelRecurring

[KarinG]

WIP - my ITEM 3:

ITEM3 - Cancelling a Recurring Contribution

1. The method doCancelRecurring() was added in CiviCRM 5.25 https://github.com/civicrm/civicrm-core/blob/master/CRM/Core/Payment.php#L1411 and is now the preferred function for Cancelling a Recurring Contribution! For older versions of CiviCRM you need to implement cancelSubscription().

2. Note: from CiviCRM 5.25 cancelSubscription() will receive a \Civi\Payment\PropertyBag and NOT an array. So -> if you are using array_ functions to interact with the $params that will no longer work as it is no longer an array. If you don't use array_ functions in your cancelSubscription() you will require no change! Note you can cast a $params array to $propertyBag to take advantage of it already.

3. The payment class should implement the following methods:

protected function supportsCancelRecurring() { return TRUE; } CiviCRM will show cancellation links based on this. 

4. Examples:
Fancy example: Stripe implementation -> https://lab.civicrm.org/extensions/stripe/-/blob/6.4.1/CRM/Core/Payment/Stripe.php#L975

Simple example: iATSPayments -> added a new function doCancelRecurring() & marked cancelSubscription() as to be deprecated in future [this PR]

If you are supporting ESR -> note that current ESR is 5.27 but many sites will still be on 5.21.x b/c there has not been a security advisory (yet). 

[KarinG]

@adixon - this is also a PR based on conversations w/ @eileenmcnaughton