feat: ParallelAgentRunner

[priyansh4320]

Why are these changes needed?

This PR introduces a new ParallelAgentRunner Class which let's you run your agents in parallel.
The ParallelAgentRunner adds native parallel execution capabilities to AG2, allowing multiple agents to run concurrently.

Basic Task Structure:

from autogen import ParallelAgentRunner

# Create a parallel runner
parallel_runner = ParallelAgentRunner(
    max_workers=8,  # or use default calculation
    timeout=300,    # 5 minutes per task
    handle_errors='collect'  # 'collect', 'fail_fast', or 'ignore'
)

# Define parallel tasks
tasks = [
    {
        'name': 'symptom_analysis',
        'agent_config': {...},
        'prompt': 'Analyze patient symptoms...'
    },
    {
        'name': 'drug_interaction',
        'agent_config': {...},
        'prompt': 'Check drug interactions...'
    }
]

# Execute in parallel
results = parallel_runner.run(tasks)

Related issue number

Checks

• I've included any doc changes needed for https://docs.ag2.ai/. See https://docs.ag2.ai/latest/docs/contributor-guide/documentation/ to build and test documentation locally.
• I've added tests (if relevant) corresponding to the changes introduced in this PR.
• I've made sure all auto checks have passed.

[codecov]

Codecov Report

❌ Patch coverage is 35.29412% with 66 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
autogen/agentchat/run_parallel_agents.py	35.29%	66 Missing ⚠️

Files with missing lines	Coverage Δ
autogen/agentchat/run_parallel_agents.py	35.29% <35.29%> (ø)

... and 41 files with indirect coverage changes

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