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

integrations/mysql.ini.tmpl

@@ -10,6 +10,9 @@ PASSWD   = {{TEST_MYSQL_PASSWORD}}
 SSL_MODE = disable
 PATH     = data/gitea.db
 
+[indexer]
+ISSUE_INDEXER_PATH = integrations/indexers-mysql/issues.bleve
+
 [repository]
 ROOT = integrations/gitea-integration-mysql/gitea-repositories