Add support for large dense vector properties and dense vector search

[Rahien]

This takes a slightly different approach from https://github.com/mu-semtech/mu-search/tree/feature/dense-vector because:

• the vectors are larger than in the original feature branch
• elastic search now has kNN search which is much more efficient than the custom script function used in the previous approach

For more details, see the readme file

This branch includes the work to bump ES to 9.2.0 as the kNN search requires a version bump: #102