Add image changes reports for extra sysexts

[krnowak]

Currently we generate three extra sysext images (podman, zfs and python). Make sure we get the reports for those too.

~Needs https://github.com/flatcar/flatcar-build-scripts/pull/162 first.~

CI: Tested together with #2230.

[krnowak]

Seems to be working: against last nightly, arm64: http://jenkins.infra.kinvolk.io:8080/job/container/job/image_changes/6864/consoleText against last release, arm64: http://jenkins.infra.kinvolk.io:8080/job/container/job/image_changes/6865/consoleText against last nightly, amd64: http://jenkins.infra.kinvolk.io:8080/job/container/job/image_changes/6866/consoleText against last release, amd64: http://jenkins.infra.kinvolk.io:8080/job/container/job/image_changes/6867/consoleText

[github-actions[bot]]

Build action triggered: https://github.com/flatcar/scripts/actions/runs/10635554798

[krnowak]

Kicked off another batch (to make sure it works; I also added a commit that simplifies two bits of code):

against last nightly, arm64: http://jenkins.infra.kinvolk.io:8080/job/container/job/image_changes/6872/ against last release, arm64: http://jenkins.infra.kinvolk.io:8080/job/container/job/image_changes/6873/ against last nightly, amd64: http://jenkins.infra.kinvolk.io:8080/job/container/job/image_changes/6874/ against last release, amd64: http://jenkins.infra.kinvolk.io:8080/job/container/job/image_changes/6875/

[krnowak]

Thanks.