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>

seediso/rocky9/user-data

@@ -0,0 +1,18 @@
+#cloud-config
+preserve_hostname: false
+manage_etc_hosts: true
+ssh_pwauth: true
+
+users:
+  - name: guofang
+    gecos: Guofang
+    groups: [wheel]
+    shell: /bin/bash
+    sudo: "ALL=(ALL) NOPASSWD: ALL"
+    lock_passwd: false
+    ssh_authorized_keys:
+      - @SSH_PUBKEY@
+    hashed_passwd: $6$0NtCERV3eO12t9oJ$nlFE2sSc66nFfuD5X0xMnOla1cuzOnHfeGNRY5X7dCDHg.WzWVmuRe7M17Puj44.eCWLnJAWt4WNjd9vP9X0D0
+
+chpasswd:
+  expire: false