Add sync search support for embedded mode elasticsearch

• Type: Bug
• Status: Closed
• Resolution: Fixed
• Affects Version/s: Master
• Fix Version/s: 7.0.0 DXP FP21, 7.0.0 DXP SP4, 7.0.X EE, 7.1.X, Master
• Component/s: Performance, Search Infrastructure, Search Infrastructure > Elasticsearch Connector
• Labels:
  • liferay-digital-enterprise-70-sp4
  • liferay-fixpack-de-21-7010
• Branch Version/s:
  7.0.x
• Backported to Branch:
  Committed
• Story Points: 1
• Git Pull Request: https://github.com/brianchandotcom/liferay-portal/pull/48751

When running in elasticsearch embedded mode, there is no reason to go through search threadpool dispatching. Because everything runs in the same jvm, rather than going to remote server. And we always synchronously getting the SearchResponse back, rather than using a Future. There will be better performance if we just let the invoker thread perform the search task directly.