AlertingNG: POC of evaluator under feature flag. (#27922)

* New feature toggle for enabling alerting NG

* Initial commit

* Modify evaluate alert API request

* Check for unique labels in alert execution result dataframes

* Remove print statement

* Additional minor fixes/comments

* Fix lint issues

* Add API endpoint for evaluating panel queries

* Push missing renaming

* add refId for condition to API

* add refId for condition to API

* switch dashboard based eval to get method

* add from/to params to dashboard based eval

* add from/to params to  eval endpoint

Co-authored-by: kyle <kyle@grafana.com>

pkg/api/dtos/ngalert.go

@@ -0,0 +1,12 @@
+package dtos
+
+import (
+	"time"
+
+	eval "github.com/grafana/grafana/pkg/services/ngalert"
+)
+
+type EvalAlertConditionsCommand struct {
+	Conditions eval.Conditions `json:"conditions"`
+	Now        time.Time       `json:"now"`
+}