Support Pinecone's hybrid vectors

[yasyf]

Is your feature request related to a problem? Please describe. Recently, Pinecone announced support for Sparse-dense embeddings, allowing for hybrid vector search (both semantic and keyword search). However, haystack doesn't currently support these.

Describe the solution you'd like Native support for sparse-dense vectors!

Describe alternatives you've considered I've created a small package called haystack-hybrid-embedding which can be installed to support hybrid vectors for now, but it's a hack!