vectorstores/pinecone: update pinecone connection with host field

[andrewyang17]

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This pull request addresses two bugs identified in issue #779:

1. Unexpected Status Code (400) Bug:

• Users were encountering a status code 400 error indicating the need to provide a model parameter (openai.WithEmbeddingModel("text-embedding-ada-002")) when constructing the openai type from the openai package. This PR resolves this issue by updating the pinecone_test.go file to include the required model parameter.

2. Unauthorized Response Bug:

• After adding documents into Pinecone with the embedding option, users were receiving an unauthorized response. This was due to an incorrect API usage from the WithProjectName() function. Pinecone requires a projectID, not a projectName. The quickest way to fix this is to replace the option of WithProjectName() with WithProjectID(). But I think this construction is redundant when it is used together with WithIndexName() and WithEnvironment() solely for constructing the Pinecone's endpoints. So this PR introduced WithHost() option, which the host can be easily obtained when creating index database in Pinecone.