### What problem does this PR solve?
The Aliyun Go driver has a stub `Rerank` method that always returns
`"Aliyun, Rerank not implemented"`. DashScope exposes an
OpenAI-compatible rerank endpoint (`compatible-mode/v1/rerank`) and
hosts dedicated bilingual rerankers (`gte-rerank-v2`, `gte-rerank`) that
are a natural pairing with the embedding models already in
`aliyun.json`. Without this, Aliyun users cannot use reranking within
RAGFlow.
Closes#14675
### Type of change
- [x] New Feature (non-breaking change which adds functionality)