tools: Add script to generate all test cases in VMs

Add the `generate-all-test-cases` tool, which generates all defined image
test cases based on provided "distro x arch x image-type" combination
matrix and CLI arguments. Test cases are generated by running the
`generate-test-cases` tool inside an architecture-specific VM.

The tool requires a qcow2 image to be provided for each requested
architecture. These images are used to create ephemeral VMs used
for test case generation.

There appears to be an issue with entropy on all VMs for other
architecture than the host's one. It makes the generation of the first
test case usually fail due to the `go get` command failing with a "TLS
handshake timeout" error. There is a workaround to retry the generation
of a test case a maximum of 3 times in this case. In the usual case,
the test case generation passes on the second try. All subsequent test
case generations should complete successfully on the first try.

Add the `distro-arch-imagetype-map.json` file as the default source of
the "distro x arch x image-type" combination matrix for generating test
cases. Its content is based on the current content of the
`test/data/manifests` directory.

Update `test/README.md` to mention the `generate-all-test-cases` tool.
Add a note, that `generate-test-cases` must be run on a host with the
same architecture, as the intended test case's.

Known issues:
- The tool does not work with RHEL images because of missing "9p"
  filesystem support.

Signed-off-by: Tomas Hozza <thozza@redhat.com>

tools/deploy/gen-test-data/files/run/provision-scripts/deploy.sh

@@ -0,0 +1,9 @@
+#!/bin/bash
+
+set -euxo pipefail
+
+dnf -y install  osbuild \
+                osbuild-selinux \
+                osbuild-ostree \
+                osbuild-composer \
+                golang

tools/deploy/gen-test-data/user-data.yml

@@ -0,0 +1,20 @@
+#cloud-config
+yum_repos:
+  # Fetch osbuild packages from a repository served on the host.
+  #
+  # In qemu user networking, 10.0.2.2 always points to the host:
+  # https://wiki.qemu.org/Documentation/Networking#User_Networking_.28SLIRP.29
+  osbuild:
+    name: osbuild
+    baseurl: "http://10.0.2.2:8000"
+    enabled: true
+    gpgcheck: false
+    skip_if_unavailable: true
+user: admin
+password: foobar
+ssh_pwauth: True
+chpasswd:
+  expire: False
+sudo: 'ALL=(ALL) NOPASSWD:ALL'
+runcmd:
+  - /run/provision-scripts/deploy.sh