Graph: support setting field units (#26529)

(cherry picked from commit ad5f1c953b)

public/app/plugins/panel/graph/axes_editor.html

@@ -13,7 +13,10 @@
 
     <div ng-if="yaxis.show">
       <div class="gf-form gf-form--grow">
-        <label class="gf-form-label width-6">Unit</label>
+        <label class="gf-form-label width-6">
+          Unit
+				  <info-popover mode="right-normal">The default unit used when not defined by the datasource or in the Fields or Overrides configuration.</info-popover>
+        </label>
         <unit-picker onChange="ctrl.setUnitFormat(yaxis)" value="yaxis.format" class="flex-grow-1" />
       </div>
     </div>

public/app/plugins/panel/graph/module.ts

@@ -306,6 +306,7 @@ export class GraphCtrl extends MetricsPanelCtrl {
     for (const series of this.seriesList) {
       series.applySeriesOverrides(this.panel.seriesOverrides);
 
+      // Always use the configured field unit
       if (series.unit) {
         this.panel.yaxes[series.yaxis - 1].format = series.unit;
       }
@@ -379,6 +380,7 @@ export const plugin = new PanelPlugin<GraphPanelOptions, GraphFieldConfig>(null)
   .useFieldConfig({
     standardOptions: [
       FieldConfigProperty.DisplayName,
+      FieldConfigProperty.Unit,
       FieldConfigProperty.Links, // previously saved as dataLinks on options
     ],
   })