Support VFS for fulltext index. (infiniflow#1546)

### What problem does this PR solve?

Support VFS for fulltext index, and fix some bug in vfs cleanup.

### Type of change

- [x] Bug Fix (non-breaking change which fixes an issue)
- [x] New Feature (non-breaking change which adds functionality)
- [x] Refactoring

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Co-authored-by: Ma-cat <1054638297@qq.com>