Update README and benchmark reports to reflect consistency improvements and performance metrics

- Changed data consistency description in README from "100% data consistency" to "bounded-staleness consistency" with a ~1 second validation interval.
- Updated benchmark results in README and BENCHMARK_REPORT.md to reflect new performance metrics, including throughput improvements and cache benefits.
- Revised cache consistency section to clarify the new mtime validation process and its impact on staleness.
- Adjusted benchmark summary and CSV files to include updated performance data across various file sizes and environments.