Alerting: Improve validation of query and expressions on rule submit (#53258)

* Improve error messages of server-side expression 
* move validation of alert queries and a condition to eval package

pkg/services/ngalert/api/api_testing_test.go

@@ -70,6 +70,7 @@ func TestRouteTestGrafanaRuleConfig(t *testing.T) {
 
 			evaluator := &eval.FakeEvaluator{}
 			var result []eval.Result
+			evaluator.EXPECT().Validate(mock.Anything, mock.Anything, mock.Anything).Return(nil)
 			evaluator.EXPECT().ConditionEval(mock.Anything, mock.Anything, mock.Anything, mock.Anything).Return(result)
 
 			srv := createTestingApiSrv(ds, ac, evaluator)
@@ -86,6 +87,7 @@ func TestRouteTestGrafanaRuleConfig(t *testing.T) {
 			require.Equal(t, http.StatusOK, response.Status())
 
 			evaluator.AssertCalled(t, "ConditionEval", mock.Anything, mock.Anything, mock.Anything, mock.Anything)
+			evaluator.AssertCalled(t, "Validate", mock.Anything, mock.Anything, mock.Anything)
 		})
 	})
 
@@ -110,6 +112,7 @@ func TestRouteTestGrafanaRuleConfig(t *testing.T) {
 
 			evaluator := &eval.FakeEvaluator{}
 			var result []eval.Result
+			evaluator.EXPECT().Validate(mock.Anything, mock.Anything, mock.Anything).Return(nil)
 			evaluator.EXPECT().ConditionEval(mock.Anything, mock.Anything, mock.Anything, mock.Anything).Return(result)
 
 			srv := createTestingApiSrv(ds, ac, evaluator)
@@ -125,6 +128,7 @@ func TestRouteTestGrafanaRuleConfig(t *testing.T) {
 
 			require.Equal(t, http.StatusUnauthorized, response.Status())
 			evaluator.AssertNotCalled(t, "ConditionEval", mock.Anything, mock.Anything, mock.Anything, mock.Anything)
+			evaluator.AssertNotCalled(t, "Validate", mock.Anything, mock.Anything, mock.Anything)
 
 			rc.IsSignedIn = true
 
@@ -140,6 +144,7 @@ func TestRouteTestGrafanaRuleConfig(t *testing.T) {
 			require.Equal(t, http.StatusOK, response.Status())
 
 			evaluator.AssertCalled(t, "ConditionEval", mock.Anything, mock.Anything, mock.Anything, mock.Anything)
+			evaluator.AssertCalled(t, "Validate", mock.Anything, mock.Anything, mock.Anything)
 		})
 	})
 }