Integrate with Google Vertex AI Vector DBs

[johnsutor]

Is your feature request related to a problem? Please describe.
It would be nice to be able to take full advantage of Vertex AI Vector DB offerings, including Vector Search, BigQuery, and AlloyDB. There is a module for BigQuery Vector Search, but it doesn't appear to be officially supported (based on the ReadMe Supported VectorStores)

Describe the solution you'd like
I would like to have adapters for using these vector databases with Vanna AI. I am more than happy to implement these, as there are already LangChain adapters available to use these offerings.

Describe alternatives you've considered
I have not considered any alternatives as these are new features.

Additional context
As mentioned, I am happy to implement these.