Add support for MultiVector search

[dirkkul]

There are tests that show the syntax here:

https://github.com/weaviate/weaviate/blob/f2269c2563e937d6ec82dd917ab3cc7bac428190/adapters/handlers/graphql/local/get/get_test.go#L1407

go client PR for reference: https://github.com/weaviate/weaviate-go-client/pull/239

image with support: semitechnologies/weaviate:preview-allow-multiple-inputs-for-a-single-target-vector-b6785b6 (or latest main)