Emails Not Sent When Destination Is Explicitly Set; Require Support for Both Assignees and Owners as Alert Recipients

[Siddhanttimeline]

1. When explicitly setting email addresses as the destination for alerts, the emails are not being sent. However, if the destination is set to "Assignees," the emails are delivered successfully. This indicates an issue with the handling of explicitly set email destinations.
2. Currently, the alert configuration allows selecting either "Assignees" or "Owners" as recipients, but not both. We should enhance this functionality to allow users to select both "Assignees" and "Owners" simultaneously as alert recipients.