#### What type of PR is this? /kind improvement /kind api-change /area core #### What this PR does / why we need it: See https://github.com/JohnNiang/halo/blob/refactor/search/docs/extension-points/search-engine.md for more #### Which issue(s) this PR fixes: Fixes https://github.com/halo-dev/halo/issues/5202 Fixes https://github.com/halo-dev/halo/issues/5339 Fixes https://github.com/halo-dev/halo/issues/5613 Fixes https://github.com/halo-dev/halo/issues/5172 Fixes https://github.com/halo-dev/halo/issues/4796 Fixes https://github.com/halo-dev/halo/issues/5625 Fixes https://github.com/halo-dev/halo/issues/5805 #### Special notes for your reviewer: #### Does this PR introduce a user-facing change? ```release-note 重构搜索引擎并提高可扩展性。 ```
