podman manifest add: support creating artifact manifest on the fly

[nalind]

Add a --artifact flag to podman manifest add which can be used to create an artifact manifest for one or more files and attach it to a manifest list. Corresponding --artifact-type, --artifact-config-type, --artifact-config, --artifact-layer-type, --artifact-subject, and --artifact-exclude-titles flags can be used to fine-tune the fields in the artifact manifest that don't refer to the files themselves.

Add --index and --subject flags to podman manifest annotate that will cause values passed to the --annotation flag to be applied to the manifest list as a whole instead of to an entry in the list, and which will add a reference to the manifest for the --subject argument.

Add a --annotation flag to podman manifest create that will cause annotations to be added to the new image index, which has the side-effect of forcing its format to be OCI from the start.

Does this PR introduce a user-facing change?

`podman manifest add` now supports `--artifact` and related flags which will create an artifact manifest for one or more files and add them to the specified manifest list.

[packit-as-a-service]

Ephemeral COPR build failed. @containers/packit-build please check.

[nalind]

/label bloat_approved

[openshift-ci]

@nalind: The label(s) /label bloat_approved cannot be applied. These labels are supported: acknowledge-critical-fixes-only, platform/aws, platform/azure, platform/baremetal, platform/google, platform/libvirt, platform/openstack, ga, tide/merge-method-merge, tide/merge-method-rebase, tide/merge-method-squash, px-approved, docs-approved, qe-approved, no-qe, downstream-change-needed, rebase/manual, cluster-config-api-changed, approved, backport-risk-assessed, bugzilla/valid-bug, cherry-pick-approved, jira/valid-bug, staff-eng-approved. Is this label configured under labels -> additional_labels or labels -> restricted_labels in plugin.yaml?

In response to this:

/label bloat_approved

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[rhatdan]

0002-Add-man-page-content-for-artifacts.patch

[packit-as-a-service]

Cockpit tests failed for commit 35cd59f. @martinpitt, @jelly, @mvollmer please check.

[mheon]

Code LGTM

[TomSweeneyRedHat]

LGTM and happy green test buttons on this 5.0 PR.

[rhatdan]

/lgtm

[nalind]

Reduced the number of flag combinations, added --artifact-config to the flags tested, and added a cleanup of the test-specific registry to the "manifest list --add --artifact" test.

[rhatdan]

/lgtm

[TomSweeneyRedHat]

@nalind now you have red tests kicking up their heels.

[nalind]

Give it a minute. Also needs a "/approve" from someone listed as an approver in the OWNERS file.

[mheon]

/approve

[openshift-ci]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: mheon, nalind

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