feat: Add connection/worker tracking and standardize metric tags

[elchinoo]

Summary

This PR enhances the StormDB plugin system with comprehensive connection/worker tracking and standardizes metric tag structures for consistent analysis.

Key Features

🔧 Database Schema Enhancement

• New Migration 004: Adds active_connections and active_workers columns to test_run_result table
• Optimized Indexes: New indexes for efficient querying by connection and worker counts
• Documentation: Clear comments explaining the purpose of new fields

📊 Core System Updates

• Enhanced TestResult struct: Added optional ActiveConnections and ActiveWorkers fields
• Updated StorageManager: Handles new fields in all CRUD operations with proper null handling
• Backward compatibility: Existing data continues to work seamlessly

🏷️ Standardized Tag Structure

Previously, metrics had inconsistent tag structures making analysis difficult. Now all metrics include:

• metric_type: Type of measurement (e.g., 'cumulative_tps', 'avg_latency_ms')
• iteration: Background save iteration (null for final results)
• connections: Number of database connections
• batch_size: Batch size (null for TPCC metrics)
• total_transactions: Total transaction count
• total_rows: Total rows processed (null for TPCC)
• batch_count: Number of batches (null for TPCC)
• test_phase: 'measurement' or 'final_results'

TPCC-specific additions:

• scale_factor: TPC-C scale factor
• transaction_type: Type of TPC-C transaction

🔄 Enhanced Plugin Functionality

Bulk-Load Plugin

• Real-time tracking: Monitors active connections and workers during execution
• Background metrics: Enhanced with connection/worker information
• Consistent tagging: All metrics follow the standardized structure

TPCC-Scalability Plugin

• Connection correlation: Links performance to connection levels
• Worker tracking: Monitors worker thread activity
• Standardized output: Consistent tag structure across all metrics

Impact

Before

-- Inconsistent tag structures made analysis difficult
{"batch_size": 100, "connections": 10, "metric_type": "avg_latency_ms"}
{"iteration": 264, "total_rows": 17844837, "connections": 10, "metric_type": "cumulative_row_rate"}
{"connections": 48, "metric_type": "total_transactions", "test_phase": "measurement"}

After

-- Consistent structure enables easy analysis
{"metric_type": "avg_latency_ms", "iteration": null, "connections": 10, "batch_size": 100, "total_transactions": 1000, "total_rows": 100000, "batch_count": 2, "test_phase": "final_results"}
{"metric_type": "cumulative_row_rate", "iteration": 264, "connections": 10, "batch_size": null, "total_transactions": 343716, "total_rows": 17844837, "batch_count": 2, "test_phase": "measurement"}

Testing

• ✅ All code compiles successfully
• ✅ Both plugins build without errors
• ✅ Core StormDB application builds successfully
• ✅ Database schema migration ready for deployment

Migration Required

After merging, run the new migration:

-- This will be applied automatically by the migration system
-- migrations/004_add_connection_worker_tracking.sql

Resolves the metrics inconsistency issues and provides comprehensive connection/worker tracking for better performance analysis.