Feat: New queries + dashboard templates

[joacoc]

This PR adds the following queries to the integration guides:

• Volume and count of messages for each source
• Volume and count of messages for each sink
• Clusters CPU and memory usage
• Sources statuses
• Sink statuses
• Storage usage
• Source snapshot

In addition, two new dashboard templates are available using this data.

Note: Queries to retrieve arrangements, or any cluster replica introspection query, are not present since each query runs only in one cluster replica.