Prometheus: Run exemplars explore queries through backend (#39531)

* Prometheus: Run Explore both queries trough backend

* Refactor, simplify

* Set default values for query type selector

* Run multiple queries as one query trough backend

* Remove trailing newlines

* Pass utcOffset

* Remove trailing comma

* WIP: Implementatioon of exemplars

* add sampling for exemplars

* Refactor to use response as custom metadata

* Simplify processing of exemplars

* Update, clean up

* Refactor the way how we get available exemplars

* Simplify exemplars disabling and running on frontend

* Add tests

* Update toggle

* Remove console log

* Fix go linting

* Fix e2e test

* Trigger Build

* Compare lengts, small fix

* Remove duplicated time check

* Address feedback

* Remove redundant ! as not needed

* Update

public/app/plugins/datasource/prometheus/components/__snapshots__/PromExploreQueryEditor.test.tsx.snap

@@ -14,9 +14,7 @@ exports[`PromExploreQueryEditor should render component 1`] = `
         }
       }
       onChange={[MockFunction]}
-      onKeyDownFunc={[Function]}
-      onQueryTypeChange={[Function]}
-      onStepChange={[Function]}
+      onRunQuery={[MockFunction]}
       query={
         Object {
           "expr": "",
@@ -24,8 +22,6 @@ exports[`PromExploreQueryEditor should render component 1`] = `
           "refId": "A",
         }
       }
-      queryType="both"
-      stepValue="1s"
     />
   }
   data={

public/app/plugins/datasource/prometheus/components/__snapshots__/PromQueryEditor.test.tsx.snap

@@ -176,9 +176,16 @@ exports[`Render PromQueryEditor with basic options should render 1`] = `
             "getPrometheusTime": [MockFunction],
           }
         }
-        isEnabled={true}
         onChange={[Function]}
-        refId="A"
+        query={
+          Object {
+            "exemplar": true,
+            "expr": "",
+            "interval": "",
+            "legendFormat": "",
+            "refId": "A",
+          }
+        }
       />
     </div>
   }