Add Google Vertex nearest neighbour search based document store

[lalitpagaria]

Google vertex based document store will add value to Haystack users.

https://cloud.google.com/blog/products/ai-machine-learning/vertex-matching-engine-blazing-fast-and-massively-scalable-nearest-neighbor-search

Sample notebook: https://github.com//GoogleCloudPlatform/ai-platform-samples/blob/master/ai-platform-unified/notebooks/unofficial/matching_engine/matching_engine_for_indexing.ipynb

Matching engine docs: https://cloud.google.com/vertex-ai/docs/matching-engine

[brandenchan]

Awesome to see so much interesting in vector storage engines right now. Clearly this is a very active area of research and development. We're always open to contributions for new components.

[mathew55]

This looks interesting, I will try to spent some time on this in the coming days...!

[dbg-raghulkrishna]

is the any update on this?