Inspector: find the datasource from the refId, not the metadata (#22231)

* remove datasource

* get datasoure from refId

* metrictank does not need to say the datasource

packages/grafana-data/src/types/data.ts

@@ -20,10 +20,6 @@ export interface QueryResultMeta {
   // Used in Explore to show limit applied to search result
   limit?: number;
 
-  // HACK: save the datassource name in the meta so we can load it from the response
-  // we should be able to find the datasource from the refId
-  datasource?: string;
-
   // DatasSource Specific Values
   custom?: Record<string, any>;
 }