Enable updating the pinecone vector store namespace

[adambchouti]

When using pinecone, it would be nice to not have to create a new vectorStore instance for different namespaces. This PR is to simply:

• add a setter to update the pinecone namespace used during requests
• Add additional functions that allow passing a custom namespace during add, search and delete

[adambchouti]

Probably best to just pass the namespace as a parameter when adding, searching and removing from the vector store

[markpollack]

Thanks for this. I've created this issue #209 to better understand the APIs of vector store providers. Ideally I would like a mechanism to pass vector store provider options to each implementation in a generic way so that casting to a subtype of VectorStore is not required. See the issue for more context.

[adambchouti]

Makes perfect sense, gonna close this one. Thx a lot!

[tzolov]

merged at 36278af