Update stack to latest Event Notifications DA and handle the support for COS integration #9
Description
Once terraform-ibm-modules/terraform-ibm-event-notifications#157 is merged the DA will by default be integrated with COS which is used for collecting failed events.
The code allows you to create a COS bucket in an existing COS instance, so lets use the instance that is created by the Observability DA, and use the Key Protect instance created by KMS DA to allow it to create a root key for bucket encryption.