build: build all images + run tests using them (#1069)

TODO

 Add patches
 Figure out why cache misses for Git clone (or something else)
diff --git a/images/magnum/Dockerfile b/images/magnum/Dockerfile
new file mode 100644
index 0000000..f945cf1
--- /dev/null
+++ b/images/magnum/Dockerfile
@@ -0,0 +1,45 @@
+# Copyright (c) 2024 VEXXHOST, Inc.
+#
+# Licensed under the Apache License, Version 2.0 (the "License"); you may
+# not use this file except in compliance with the License. You may obtain
+# a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+# License for the specific language governing permissions and limitations
+# under the License.
+
+FROM registry.atmosphere.dev/library/ubuntu:zed AS helm
+ARG TARGETOS
+ARG TARGETARCH
+ARG HELM_VERSION=3.14.0
+ADD https://get.helm.sh/helm-v${HELM_VERSION}-${TARGETOS}-${TARGETARCH}.tar.gz /helm.tar.gz
+RUN tar -xzf /helm.tar.gz
+RUN mv /${TARGETOS}-${TARGETARCH}/helm /usr/bin/helm
+
+FROM registry.atmosphere.dev/library/openstack-venv-builder:zed AS build
+ARG MAGNUM_GIT_REF=0ee979099a01ae2c8b1b5d6757897a8993e4e34c
+ADD --keep-git-dir=true https://opendev.org/openstack/magnum.git#${MAGNUM_GIT_REF} /src/magnum
+RUN git -C /src/magnum fetch --unshallow
+COPY patches/magnum /patches/magnum
+RUN git -C /src/magnum apply --verbose /patches/magnum/*
+RUN --mount=type=cache,mode=0755,target=/root/.cache/pip,sharing=private <<EOF bash -xe
+pip3 install \
+    --constraint /upper-constraints.txt \
+        /src/magnum \
+        magnum-cluster-api==0.16.0
+EOF
+
+FROM registry.atmosphere.dev/library/openstack-python-runtime:zed
+RUN <<EOF bash -xe
+apt-get update -qq
+apt-get install -qq -y --no-install-recommends \
+    haproxy
+apt-get clean
+rm -rf /var/lib/apt/lists/*
+EOF
+COPY --from=helm --link /usr/bin/helm /usr/local/bin/helm
+COPY --from=build --link /var/lib/openstack /var/lib/openstack