Is your feature request related to a problem? Please describe.

Developers who want to use Vertex Vector Search as a scalable, production-ready solution don't have a way to do so through Genkit.

Describe the solution you'd like

Make Vertex Vector Search available through the Vertex AI plugin as indexer and retriever components.

Describe alternatives you've considered

Developers can define their own indexer and retriever components, but it's more convenient to have it exposed through the plugin as a first class experience.

Additional context

More info on Vertex Vector Search available here: https://cloud.google.com/vertex-ai/docs/vector-search/overview