feat: add variable for datasource in grafana dashboards (#21470)

docs/metrics/prometheus/grafana/minio-dashboard.json

@@ -21,16 +21,6 @@
       }
     ]
   },
-  "__inputs": [
-    {
-      "name": "DS_PROMETHEUS",
-      "label": "Prometheus",
-      "description": "", 
-      "type": "datasource",
-      "pluginId": "prometheus",
-      "pluginName": "Prometheus"
-    }
-  ],
   "description": "MinIO Grafana Dashboard - https://min.io/",
   "editable": true,
   "fiscalYearStartMonth": 0,
@@ -3800,6 +3790,20 @@
   ],
   "templating": {
     "list": [
+      {
+        "current": {
+          "selected": false,
+          "text": "All",
+          "value": "$__all"
+        },
+        "label": "Data source",
+        "name": "DS_PROMETHEUS",
+        "options": [],
+        "query": "prometheus",
+        "refresh": 1,
+        "regex": "",
+        "type": "datasource"
+      },
       {
         "current": {
           "selected": false,
@@ -3861,4 +3865,4 @@
   "uid": "TgmJnqnnk",
   "version": 1,
   "weekStart": ""
-}
+}