Remove searchEngine from App (#18540)

https://community-daily.mattermost.com/boards/workspace/zyoahc9uapdn3xdptac6jb69ic/285b80a3-257d-41f6-8cf4-ed80ca9d92e5/495cdb4d-c13a-4992-8eb9-80cfee2819a4?c=c6753a1c-dbbf-4316-8e4e-c58ebb65d6e0

```release-note
NONE
```

app/app.go

@@ -26,11 +26,6 @@ import (
 
 type App struct {
 	srv *Server
-
-	// XXX: This is required because removing this needs BleveEngine
-	// to be registered in (h *MainHelper) setupStore, but that creates
-	// a cyclic dependency as bleve tests themselves import testlib.
-	searchEngine *searchengine.Broker
 }
 
 func New(options ...AppOption) *App {
@@ -508,7 +503,7 @@ func (a *App) DataRetention() einterfaces.DataRetentionInterface {
 	return a.srv.DataRetention
 }
 func (a *App) SearchEngine() *searchengine.Broker {
-	return a.searchEngine
+	return a.srv.SearchEngine
 }
 func (a *App) Ldap() einterfaces.LdapInterface {
 	return a.srv.Ldap

app/options.go

@@ -109,6 +109,5 @@ type AppOptionCreator func() []AppOption
 func ServerConnector(s *Server) AppOption {
 	return func(a *App) {
 		a.srv = s
-		a.searchEngine = s.SearchEngine
 	}
 }

app/searchengine.go

@@ -32,7 +32,7 @@ func (a *App) TestElasticsearch(cfg *model.Config) *model.AppError {
 }
 
 func (a *App) SetSearchEngine(se *searchengine.Broker) {
-	a.searchEngine = se
+	a.srv.SearchEngine = se
 }
 
 func (a *App) PurgeElasticsearchIndexes() *model.AppError {