[FEATURE] currently there is no way to display all emails in the "to" field for an email channel

[guillaumeldc]

Is your feature request related to a problem?
It would be great to have the ability to display all email destinations of a notification in the "to" field. Currently only the distribution list or the own user email address is shown.

What solution would you like?
A check box when creating the notification channel that give the ability to choose whether or not to hide email addresses from the "to" field.

What alternatives have you considered?
In the alerting plugin, if we can have access to the channel variables, we could modify the mustache template to display the list of emails the notification was sent to.

[AWSHurneyt]

@amsiglan @sbcd90 could you transfer this to https://github.com/opensearch-project/dashboards-notifications/issues