feat(vdb): add HNSW vector index for TiDB vector store with TiFlash

[bowenliang123]

Summary

• to close feat: add HNSW vector index for TiDB vector store #12332
• Add the HNSW vector index in TiDB VDB for embeeding column
  • Vector Column Index requires the service and replicas of TiFlash
  • doc: https://docs.pingcap.com/tidb/stable/vector-search-index#create-the-hnsw-vector-index
• Update TiDB images from v8.4.0 (Development Milestone Releases, DMR) to v8.5.x (Long-Term Support Releases, LTS)

Screenshots

Checklist

Important

Please review the checklist below before submitting your pull request.

• This change requires a documentation update, included: Dify Document
• I understand that this PR may be closed in case there was no previous discussion or issues. (This doesn't apply to typos!)
• I've added a test for each change that was introduced, and I tried as much as possible to make a single atomic change.
• I've updated the documentation accordingly.
• I ran dev/reformat(backend) and cd web && npx lint-staged(frontend) to appease the lint gods

[bowenliang123]

Hi, is there any blocking issue or advice for this PR? Feel free to ask me to follow. cc @JohnJyong @laipz8200

[breezewish]

Thank you! Some comments about the most recent Vector Index syntax.

[bowenliang123]

Thanks for the detailed reviews from TiDB Team! Will have feedback code changes soon.

[bowenliang123]

Resolved all the comments.