PanelEdit: Add data source label to data source picker dropdown (#34605)

* PanelEdit: Add data source label to data source picker dropdown

* Updated based on ux feedback

public/app/features/query/components/QueryGroup.tsx

@@ -6,6 +6,7 @@ import {
   CustomScrollbar,
   HorizontalGroup,
   Icon,
+  InlineFormLabel,
   Modal,
   ScrollbarPosition,
   stylesFactory,
@@ -201,6 +202,7 @@ export class QueryGroup extends PureComponent<Props, State> {
     return (
       <div>
         <div className={styles.dataSourceRow}>
+          <InlineFormLabel width={'auto'}>Data source</InlineFormLabel>
           <div className={styles.dataSourceRowItem}>
             <DataSourcePicker
               onChange={this.onChangeDataSource}