feat: add delete all documents to Pineconde DocumentStore

[ChinmayBansal]

Related Issues

• fixes add delete_all_documents() operation to PineconeDocumentStore #2317

Proposed Changes:

Added delete_all_documents() and delete_all_documents_async() methods to PineconeDocumentStore to enable deletion of all documents from an index namespace.

Implementation details:

• Both sync and async versions implemented following the existing delete_documents() pattern
• Uses Pinecone's native index.delete(delete_all=True, namespace=...) API
• Follows the reference implementation from OpenSearch DocumentStore PR feat: adding the operation delete_all_documents to the OpenSearchDocumentStore #2321

Files changed:

• document_store.py: Added both methods
• test_document_store.py: Added 2 sync integration tests
• test_document_store_async.py: Added 2 async integration tests

How did you test it?

• ✅ Unit tests: hatch run test:unit - 17 passed
• ✅ Integration tests: Added 4 new integration tests (2 sync + 2 async):
  • test_delete_all_documents: Verifies deletion of multiple documents
  • test_delete_all_documents_empty_collection: Verifies behavior with empty collection
  • test_delete_all_documents_async: Async version with multiple documents
  • test_delete_all_documents_async_empty_collection: Async version with empty collection

Notes for the reviewer

• Implementation follows the pattern established in OpenSearch PR feat: adding the operation delete_all_documents to the OpenSearchDocumentStore #2321 (reference implementation for parent issue #8508)
• Uses Pinecone's native delete_all=True parameter which efficiently deletes all vectors in the specified namespace
• Consistent with existing delete_documents() method in the same file
• No recreate_index parameter needed - Pinecone handles index management differently than search engines

Checklist

• I have read the contributors guidelines and the code of conduct
• I have updated the related issue with new insights and changes
• I added unit tests and updated the docstrings
• I've used one of the conventional commit types for my PR title: fix:, feat:, build:, chore:, ci:, docs:, style:, refactor:, perf:, test:.