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_ruler_test.go

@@ -646,7 +646,6 @@ func createService(ac *acMock.Mock, store *store.FakeRuleStore, scheduler schedu
 	return &RulerSrv{
 		xactManager:     store,
 		store:           store,
-		DatasourceCache: nil,
 		QuotaService:    nil,
 		provenanceStore: provisioning.NewFakeProvisioningStore(),
 		scheduleService: scheduler,