feat(storage): add run_benchmark_tests.sh for automated time-based GC…

[shradhakatyal]

• Adds run_benchmark_tests.sh under packages/google-cloud-storage/cloudbuild/ to automate high-bandwidth GCS read microbenchmarks for large objects (10 GiB file sizes).
• Dynamically updates config.yaml to test multi-process worker pools (PROCESSES=48) across standard REST and BidiReadObject DirectPath gRPC (zonal buckets).
• Automatically verifies and pre-seeds required GCS test objects prior to benchmark execution to ensure consistent benchmark conditions.
• Emits structured JSON metrics via --benchmark-json for automated ingestion into Cloud Build CI

[gemini-code-assist]

Code Review

This pull request introduces an automated Google Cloud Storage read microbenchmark runner script (run_benchmark_tests.sh) designed for GitHub CI/CD and high-bandwidth GCE VMs. The review feedback identifies two critical areas for improvement: first, a race condition and a NameError in the Python pre-seeding block where concurrent processes attempt to write to the same payload file and reference an undefined variable; second, a style guide violation where the configuration loaded from config.yaml is not type-validated before indexing.