[FEATURE] Support Multiple Data Source in Alerting Dashboards Plugin

[BionIT]

Is your feature request related to a problem?
With multiple data source enabled, users of OpenSearch Dashboards are able to create data source connections and query local and remote OpenSearch clusters. Enabling multiple data source at dashboards plugin would ensure users that have been using the multiple data source feature to have a consistent experience in the dashboard, and allows users to use the same dashboard for different clusters.

What solution would you like?
Support multiple data source in the Alerting dashboards plugin and allow user to use one alerting dashboard for different backend clusters

What alternatives have you considered?
User would need to create a new Opensearch dashboard with alerting plugin enabled for each cluster

Do you have any additional context?
Add any other context or screenshots about the feature request here.

[BionIT]

@riysaxen-amzn Just closed the issue since the PR is merged and backported, please re-open if any