Alerting: Rule backtesting with experimental UI (#115525)

* add function to convert StateTransition to LokiEntry
* add QueryResultBuilder
* update backtesting to produce result similar to historian
* make shouldRecord public
* filter out noop transitions
* add experimental front-end
* add new fields
* move conversion of api model to AlertRule to validation
* add extra labels
* calculate tick timestamp using the same logic as in scheduler
* implement correct logic of calculating first evaluation timestamp
* add uid, group and folder uid they are needed for jitter strategy

* add JitterOffsetInDuration and JitterStrategy.String()

* add config `backtesting_max_evaluations` to [unified_alerting] (not documented for now)

* remove obsolete tests

* elevate permisisons for backtesting endpoint
* move backtesting to separate dir

pkg/services/ngalert/api/api.go

@@ -161,7 +161,7 @@ func (api *API) RegisterAPIEndpoints(m *metrics.API) {
 			authz:           ruleAuthzService,
 			evaluator:       api.EvaluatorFactory,
 			cfg:             &api.Cfg.UnifiedAlerting,
-			backtesting:     backtesting.NewEngine(api.AppUrl, api.EvaluatorFactory, api.Tracer),
+			backtesting:     backtesting.NewEngine(api.AppUrl, api.EvaluatorFactory, api.Tracer, api.Cfg.UnifiedAlerting, api.FeatureManager),
 			featureManager:  api.FeatureManager,
 			appUrl:          api.AppUrl,
 			tracer:          api.Tracer,