Squash and rebase multiarch feature branch

Moves manifest-approach to a parallel role besides the 1.3.0 approach.

Also adds pipeline mechanics to automatically detect and handle
architecture builds.

Furthermore squashed commit of the following:

commit 1b3bd0fd
Author: Alexander Wellbrock <a.wellbrock@mailbox.org>
Date:   Sat Jan 16 16:48:26 2021 +0100

    CI: fix syntax error in CI script

commit 9ce8c0b7
Author: Alexander Wellbrock <a.wellbrock@mailbox.org>
Date:   Sat Jan 16 14:23:00 2021 +0100

    shell-tools: add test-cases for manifests

commit 02a128dc
Author: Alexander Wellbrock <a.wellbrock@mailbox.org>
Date:   Sat Jan 16 14:22:38 2021 +0100

    refactor remaining code to manifest

    Now it's fully manifest approach with the naming, thinking and
    everything.

    Makes a lot of things clearer and should help getting multiarch done.

    In theory this is sufficient going forward, since manifests can also be
    used for single-arch. In order to be backwards compatible and still
    support the simple tagging approach we can re-introduce the tagging
    part and split it by using different CI templates, while the
    build-ah-engine uses the multiarch templates.

    For compatibility reasons I'd use a new template name for multiarch in
    that case.

commit 94f91a01
Author: Alexander Wellbrock <a.wellbrock@mailbox.org>
Date:   Sat Jan 16 14:18:04 2021 +0100

    shell-tools: remove latest test

    The latest test is incompatible with the full-metadata approach.

    Could be restored, when legacy tagging is restored as well.

commit 79f9f29a
Author: Alexander Wellbrock <a.wellbrock@mailbox.org>
Date:   Fri Jan 15 22:29:49 2021 +0100

    shell-tools: go all in with manifest

    This removes all the images code and relies solely on manifests.

    The templates always create images with manifest suffix.

    What's left todo is to get rid of the pull-code and just try to add all
    built archs to the manifest directly from the remote, since it should
    be pushed to the remote anyway.

commit 8d4e70ba
Author: Alexander Wellbrock <a.wellbrock@mailbox.org>
Date:   Fri Jan 15 22:20:45 2021 +0100

    tests: remove obsolete statements from multiarch

commit 756beaf2
Author: Alexander Wellbrock <a.wellbrock@mailbox.org>
Date:   Fri Jan 15 21:33:39 2021 +0100

    shell-tools: fix inaccessible pushImageOrManifest

    The function has to be exported and used with bash -c here in order to
    work with xargs.

    See for more info:
    https://stackoverflow.com/questions/11003418/calling-shell-functions-with-xargs

commit 48974403
Author: Alexander Wellbrock <a.wellbrock@mailbox.org>
Date:   Thu Jan 14 14:37:11 2021 +0100

    disable shellcheck rule SC2015

    The rule notes that this could be mis-used as if-then-else. This is
    intended here, since the logic is not meant to be if-then-else but
    rather if-then-anyway

commit 5a6633e8
Author: Alexander Wellbrock <a.wellbrock@mailbox.org>
Date:   Thu Jan 14 14:30:46 2021 +0100

    add aarch64 build job

    Since we support the alternative name aarch64 for arm64 we should also
    provide an optional build job for it in the template.

    The build-ah-engine will per default only build amd64 and arm64

commit 6609af6a
Author: Alexander Wellbrock <a.wellbrock@mailbox.org>
Date:   Thu Jan 14 14:29:44 2021 +0100

    extend push tooling by manifest type

    The push tool will now perform a simple check if the image reference is
    of type manifest and will invoke the correct command for that.

    The --all parameter is used to push all images on the local machine
    referenced in the manifest which has shown to reduce errors at
    registries.

    The --format v2s2 tag is crucial to push the manifest in docker format
    which is the only supported format of quay.io.

commit 6b330f9e
Author: Alexander Wellbrock <a.wellbrock@mailbox.org>
Date:   Thu Jan 14 14:27:28 2021 +0100

    add si-pull tool

    The image pull is now done in it's own script file to handle the logic
    of trying different expected images and fail if none was found.

commit 5a683bc1
Author: Alexander Wellbrock <a.wellbrock@mailbox.org>
Date:   Thu Jan 14 13:30:35 2021 +0100

    Revert removal of var exports

    We don't want to break backwards compatiblity.

commit caf9812d
Author: Alexander Wellbrock <a.wellbrock@mailbox.org>
Date:   Wed Jan 13 00:57:00 2021 +0100

    fix test for manifest based build

    Don't test the tagging tools, since we already do this in a separate
    job.

commit 92719317
Author: Alexander Wellbrock <a.wellbrock@mailbox.org>
Date:   Wed Jan 13 00:56:15 2021 +0100

    pin build base image to build-ah-engine 2.0.0

commit 265caf5b
Author: Alexander Wellbrock <a.wellbrock@mailbox.org>
Date:   Wed Jan 13 00:06:55 2021 +0100

    Exclude runs on merge requests

    Reference: https://docs.gitlab.com/ee/ci/yaml/README.html#prevent-duplicate-pipelines

commit d4580afb
Author: Alexander Wellbrock <a.wellbrock@mailbox.org>
Date:   Wed Jan 13 00:00:47 2021 +0100

    add missing storage.conf

commit bc6fe549
Author: Alexander Wellbrock <a.wellbrock@mailbox.org>
Date:   Tue Jan 12 23:53:35 2021 +0100

    remove syntax error in before_script

commit 189c14fc
Author: Alexander Wellbrock <a.wellbrock@mailbox.org>
Date:   Tue Jan 12 23:49:04 2021 +0100

    fix typo in path to shell-tools

commit abdad0e1
Author: Alexander Wellbrock <a.wellbrock@mailbox.org>
Date:   Tue Jan 12 23:44:18 2021 +0100

    fix before_script execution order

    First install podman, then use it.

commit 47f90cf1
Author: Alexander Wellbrock <a.wellbrock@mailbox.org>
Date:   Tue Jan 12 23:41:25 2021 +0100

    remove arch variable

commit bd5d66d7
Author: Alexander Wellbrock <a.wellbrock@mailbox.org>
Date:   Tue Jan 12 23:37:15 2021 +0100

    setup initial clean build on plain fedora

commit 83c2cc95
Author: Alexander Wellbrock <a.wellbrock@mailbox.org>
Date:   Tue Jan 12 23:20:18 2021 +0100

    add default build archs ci variable

    Setting the default for the build-ah-engine repo to all archs and the
    templates included in other projects to amd64.

commit f1464918
Author: Alexander Wellbrock <a.wellbrock@mailbox.org>
Date:   Tue Jan 12 23:03:54 2021 +0100

    fix syntax of variables hash

commit 8017c09a
Author: Alexander Wellbrock <a.wellbrock@mailbox.org>
Date:   Tue Jan 12 23:02:11 2021 +0100

    fix tilde typo

commit 9b82e942
Author: Alexander Wellbrock <a.wellbrock@mailbox.org>
Date:   Tue Jan 12 23:00:03 2021 +0100

    shell-tools: add multiarch tagging and tests

    Behavior is to check if any multiarch tags / images are present in local
    storage and if so create a manifest instead of a normal image tag.

commit b8263166
Author: Alexander Wellbrock <a.wellbrock@mailbox.org>
Date:   Tue Jan 12 22:42:19 2021 +0100

    rewrite using gitlab templates