docs: update benchmark results with V3 analysis - main vs hashmap-alloc

Replace previous benchmark charts with comprehensive V3 analysis:
- 20 configs (c1/c8/c16/c32/c128 x Read/Write x HTTP1/HTTP2)
- 3 rounds each, 10 min/run, GATEWAY mode
- Timeline charts with throughput and P99 latency
- JFR allocation breakdown comparison
- Detailed per-round analysis of outlier patterns

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: Annie Liang