Add vector search support for fields in nested objects

[aprudhomme]

Add the ability to do a knn vector search query over fields in nested objects (documents). This is supported for both float and byte vector types.

When constructing the vector query, the parent document nested path is determined. Knn filter queries, if present, apply at the parent document level.

The DiversifyingChildren*KnnVectorQuerys are used to score the parent docs based on the best child vector similarity. These queries have been extended to allow for top k and diagnostics support.