Checkmk Werk 15951: Dashboards and graph collections: Support same graph multiple times

ID: 15951 Title: Dashboards and graph collections: Support same graph multiple times Component: metrics Level: 1 Class: Bug fix Version: 2.3.0b1 Before this werk, when adding the same graph multiple times to a dashboard or a graph collection, only one of the graphs was actually rendered. The other ones were displayed as empty frames.