Manifests: No tests for doing API manifests/imagename&images=foo

Issue Description

I noticed that in the documentation, we can pass in 'images' to the libpod/manifests/foobar?images=foo endpoint.

However, I noticed we have no tests for this? https://github.com/containers/podman/blob/main/test/apiv2/15-manifest.at

Also, we can actually create a manifest without images... even though the documentation says otherwise (shows required): https://docs.podman.io/en/latest/_static/api.html#tag/manifests/operation/ManifestCreateLibpod

Steps to reproduce the issue

N/A see https://github.com/containers/podman/blob/main/test/apiv2/15-manifest.at missing tests

Describe the results you received

N/A, missing tests.

Describe the results you expected

Tests for ?images parameter to manifests

podman info output

N/A

Podman in a container

No

Privileged Or Rootless

None

Upstream Latest Release

Yes

Additional environment details

Additional environment details

Additional information

Additional information like issue happens only occasionally or issue happens with a particular architecture or on a particular setting