RPM support: docs and AL2023/Fedora e2e validation

[ArangoGutierrez]

Follow-up from #569

The core RPM support is complete and merged. This tracks remaining work:

Documentation

• Update prerequisites to list supported RPM distributions
• Add Rocky Linux 9 setup guide / example configuration
• Add Amazon Linux 2023 guide / example configuration
• Document RPM-specific considerations (SELinux, firewalld, sudo secure_path)

E2E Validation

• Run AL2023 e2e tests (Docker, containerd, CRI-O) — test configs exist in tests/data/test_rpm_al2023_*.yml
• Run AL2023 cluster e2e test — config at tests/data/test_cluster_rpm_al2023.yaml
• Evaluate Fedora support (lower priority)

Context

• Test entries are already in aws_test.go and aws_cluster_test.go with post-merge label
• Rocky 9 is fully validated across all 3 runtimes + K8s
• AL2023 templates are in place but untested end-to-end