Improve issue search (#2387)

* Improve issue indexer

* Fix new issue sqlite bug

* Different test indexer paths for each db

* Add integration indexer paths to make clean

routers/init.go

@@ -13,7 +13,6 @@ import (
 	"code.gitea.io/gitea/models/migrations"
 	"code.gitea.io/gitea/modules/cron"
 	"code.gitea.io/gitea/modules/highlight"
-	"code.gitea.io/gitea/modules/indexer"
 	"code.gitea.io/gitea/modules/log"
 	"code.gitea.io/gitea/modules/mailer"
 	"code.gitea.io/gitea/modules/markup"
@@ -63,7 +62,7 @@ func GlobalInit() {
 
 		// Booting long running goroutines.
 		cron.NewContext()
-		indexer.NewContext()
+		models.InitIssueIndexer()
 		models.InitSyncMirrors()
 		models.InitDeliverHooks()
 		models.InitTestPullRequests()