* minor conversion improvement
* use NamedVectors in update_vectors
* remove merge from VectorStruct
* rename Multi -> Named in vector struct
* add multi-dense vectors option into VectorStruct
* generate openapi
* rename VectorStruct -> VectorStructInternal
* add conversion for anonymous multivec in grpc
* renames for BatchVectorStruct
* implement multi-dense for batch
* allow multi-dense in batch upserts
* test and fixes