Expose search service for plugin

[JohnNiang]

What type of PR is this?

/kind feature /kind api-change /area core /area plugin /milestone 2.17.0

What this PR does / why we need it:

This PR creates a SearchService and makes it invokable for plugins.

Special notes for your reviewer:

1. Create a plugin
2. Publish all publication into Maven local repository by executing ./gradlew publishAllPublicationsToMavenLocalRepository
3. Use 2.17.0-SNAPSHOT as dependency version and refresh dependencies
4. Try to use the SearchService to search something.

Does this PR introduce a user-facing change?

为插件提供全文搜索服务

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 57.95%. Comparing base (bc10336) to head (fc6af19). Report is 47 commits behind head on main.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #6239 +/- ## ============================================ + Coverage 54.51% 57.95% +3.44% - Complexity 3523 3748 +225 ============================================ Files 646 649 +3 Lines 21862 21986 +124 Branches 1528 1538 +10 ============================================ + Hits 11917 12741 +824 + Misses 9328 8626 -702 - Partials 617 619 +2 ```

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[f2c-ci-robot[bot]]

[APPROVALNOTIFIER] This PR is APPROVED

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