feat: improve pinecone tests (#2806)
Improve the integration tests for Pinecone by adding an `.env.example`
file for local testing. Additionally, add some dev dependencies
specifically for integration tests.
This change also helps me understand how Pinecone deals with certain
things, see related issues
https://github.com/hwchase17/langchain/issues/2484
https://github.com/hwchase17/langchain/issues/2816
