Add a Rocky Linux 9 virtual machine

run-rocky9.py with its QEMU config, port forwards (SSH on 2226) and
cloud-init seed, modelled on the Fedora 44 launcher. Update vm-images for
the rocky9 download target.

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

qemu/rocky9/darwin-arm64.ini

@@ -0,0 +1,24 @@
+# macOS host, arm64 part of the Rocky Linux 9 QEMU configuration; read after config.ini.
+
+# Accelerators are tried in order: HVF on macOS, else emulation.
+[accel]
+  accel = "hvf"
+
+[accel]
+  accel = "tcg"
+
+[machine]
+  type = "virt"
+
+# Unlike q35, the "virt" machine has no default GPU or USB input devices.
+[device "gpu0"]
+  driver = "virtio-gpu-pci"
+
+[device "usb0"]
+  driver = "qemu-xhci"
+
+[device "kbd0"]
+  driver = "usb-kbd"
+
+[device "tablet0"]
+  driver = "usb-tablet"