test(langchain): add benchmark tests for createAgent

[christian-bromann]

This PR adds benchmark tests for createAgent to ensure it remains performant as the codebase evolves. The benchmarks use tinybench to measure latency across various scenarios including many tools, middleware, large message histories, and complex configurations.

Motivation

As createAgent continues to evolve with new features and middleware capabilities, it's critical to have automated performance benchmarks that can catch regressions early. These benchmarks provide:

• Performance baselines for different agent configurations
• Regression detection when changes impact performance
• Visibility into how different features (tools, middleware, state schemas) affect latency

Potential additions:

• Memory usage benchmarks
• Throughput measurements (ops/sec)
• Comparison against previous runs
• Performance trend tracking over time

[changeset-bot]

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Latest commit: 859008f

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