fix(oss-opensearch): Resolve streaming crashes and improve code reliability

[akhilpathivada]

Summary

This PR enhances the OSS OpenSearch client with critical bug fixes, improved configurability, performance optimizations, and comprehensive code refactoring for better maintainability.

Key Changes

🐛 Bug Fixes

• Fix streaming insertion retry crash: Resolved crash in streaming tests during bulk insertion retries
• Fix _id field extraction: Corrected document ID extraction for accurate recall calculation
• Add cosine normalization: Proper vector normalization for cosine similarity metrics

⚙️ Configuration Enhancements

• Configurable refresh interval: Made refresh interval configurable through UI for better performance tuning

🏗️ Code Architecture Improvements

• Extract OpenSearchSettingsManager: Centralized cluster and index settings management
• Extract BulkInsertManager: Isolated bulk insertion logic with enhanced validation and error handling
• Extract SearchQueryBuilder: Clean separation of query construction logic
• Enhanced type safety: Comprehensive type hints and improved error handling
• Removed dead code: Eliminated unused get_index_setting method
• Simplified exception handling: Streamlined OpenSearchException class

📊 Impact

• Reliability: Eliminates crashes in streaming scenarios and improves error recovery
• Performance: Better configuration control and optimized bulk operations
• Maintainability: Clean architecture following SOLID principles
• Developer Experience: Better type safety and clearer code organization

Files Changed

• vectordb_bench/backend/clients/oss_opensearch/oss_opensearch.py - Core client improvements
• vectordb_bench/frontend/config/dbCaseConfigs.py - UI configuration enhancement

Testing

• Streaming insertion scenarios
• Recall calculation accuracy
• Configuration UI functionality
• Bulk insertion with various client counts

[akhilpathivada]

/assign @XuanYang-cn @alwayslove2013

[alwayslove2013]

@akhilpathivada plz fix the lint issues~

pip install black ruff --upgrade
make format
make lint

[sre-ci-robot]

[APPROVALNOTIFIER] This PR is NOT APPROVED

This pull-request has been approved by: akhilpathivada, alwayslove2013
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