Add k6 activity ramp benchmark

[rgarcia]

Summary

• add a k6 TypeScript activity-ramp benchmark for Hypeman instance lifecycle load
• add hypervisor selection and tagging for cloud-hypervisor, firecracker, and qemu matrix runs
• add a Make target that emits the local k6 HTML report and JSON summary with 120s dashboard buckets
• add CloudFormation parameters for gp3 data-volume IOPS/throughput and optional HTTP/HTTPS ingress exposure
• document benchmark inputs, shared pattern ingress behavior, and capacity rejection metrics

Validation

• docker run --rm -v "$PWD":/src -w /src grafana/k6:latest inspect benchmarks/k6/activity-ramp.ts
• go test ./... in deploy/aws/cloudformation
• make -n bench-activity-ramp HYPEMAN_API_KEY=dummy
• aws cloudformation validate-template for deploy/aws/cloudformation/template.yaml
• checked for leftover hypeman-bench CloudFormation stacks in us-east-1
• manual quickstart smoke test with nginx image, shared ingress probe, and a shortened k6 run
• full ramp run generated local HTML/JSON reports and was stopped after capacity rejections identified the target's breaking point