[FEATURE] Add parallel execution and distributed evaluation capabilities

[najeed]

Is your feature request related to a problem? Please describe.
Running evaluations on 4500+ scenarios sequentially is time-prohibitive. Users need parallel execution to complete comprehensive evaluations in reasonable timeframes, especially for enterprise use cases.

Describe the solution you'd like
Parallel and distributed evaluation system with:

1. Local Parallel Execution

   • Multi-threaded scenario processing
   • Configurable worker count
   • Resource usage monitoring
   • Progress tracking across threads

2. Distributed Evaluation

   • Worker node coordination
   • Load balancing across nodes
   • Fault tolerance and recovery
   • Result aggregation

3. Cloud Integration

   • Docker container support
   • Kubernetes deployment templates
   • AWS/GCP/Azure batch processing
   • Serverless evaluation options

Proposed API

# Local parallel execution
runner = EvaluationRunner(parallel=True, workers=8)
results = runner.evaluate_batch(scenarios, agent)

# Distributed execution
cluster = EvaluationCluster(nodes=["worker1", "worker2", "worker3"])
results = cluster.evaluate(scenarios, agent)

# Cloud execution
cloud_runner = CloudEvaluationRunner(provider="aws", instance_type="c5.xlarge")
results = cloud_runner.evaluate(scenarios, agent)

Acceptance Criteria

• Multi-threaded local execution with configurable workers
• Progress tracking and resource monitoring
• Distributed execution coordinator
• Docker containerization for workers
• Cloud deployment templates (AWS/GCP/Azure)
• Fault tolerance and automatic recovery
• Result aggregation and consistency validation

Performance Targets

• 10x speedup with 8-core local execution
• Linear scaling with distributed workers
• <5% overhead for coordination
• 99.9% result consistency between serial and parallel runs

Additional context
Essential for enterprise users who need to run comprehensive evaluations regularly. Similar to capabilities in EleutherAI/lm-evaluation-harness but optimized for agent evaluation patterns.

Estimated Effort

• Large (2+ weeks)