Install docker-buildx and dependencies

THis allows us to use a heredoc [1] in the rocky 9 image element [2].

1. https://www.docker.com/blog/introduction-to-heredocs-in-dockerfiles/
2. https://github.com/stackhpc/stackhpc-image-elements/blob/59da1ecdb73f99382e0a736bc3b03c9ed38bf892/elements/rocky-container-stackhpc/containerfiles/9-stackhpc#L20

Author: MoteHue

.github/workflows/overcloud-host-image-build.yml

@@ -212,7 +212,7 @@ jobs:
           source venvs/kayobe/bin/activate &&
           source src/kayobe-config/kayobe-env --environment ci-builder &&
           kayobe seed host command run \
-          --command "sudo apt update && sudo apt -y install gcc git libffi-dev python3-dev python-is-python3 python3-venv" --show-output
+          --command "sudo apt update && sudo apt -y install gcc git libffi-dev python3-dev python-is-python3 python3-venv containerd docker.io docker-buildx" --show-output
         env:
           KAYOBE_VAULT_PASSWORD: ${{ secrets.KAYOBE_VAULT_PASSWORD }}