feat: Add support for metadata filtering and namespaces for the Upstash Vector component

[ytkimirti]

I was planning to add Upstash support to Langflow, but I noticed that you already have it implemented, and it works quite well.

We now support namespaces and metadata filtering. We’ve added these features to the Langchain integration, and it would be great to see them in Langflow as well.

I also updated the documentation, as Upstash Vector was missing from the vector stores page.

Please let me know if any changes are needed.