Pinecone Destination : New Feature - Add `default_namespace` Config Option

[topefolorunso]

What

This PR ensures that there is strictly a namespace for airbyte to write into. Pinecone destination doesn't have great handling for namespaces. We loosely align these with the airbyte "namespace" feature - similar to databases' use of schema names and the "default_schema_name".

How

To solve this, this PR adds "Default Namespace" as a required config in the destination, and would write into this namespace when another namespace is not provided from the source and/or from the platform.

Review guide

1. indexer.py
2. config.py

User Impact

The user can choose to not define a namespace in the source or connection setting. The default namespace would be used in this case.

Can this PR be safely reverted and rolled back?

• [x] YES 💚
• [ ] NO ❌