distro: add ova image type for bootc [HMS-9503]

[mvo5]

This commit adds an image type to generate ova images from a bootc ref.

Once merged (and image-builder-cli is updated to use the new version of the images library) one can just do:

$ sudo image-builder build ova --bootc-ref quay.io/centos-bootc/centos-bootc:stream9
$ tar tvf bootc-centos-9-ova-x86_64/bootc-centos-9-ova-x86_64.ova
-rw-r--r-- root/root      5719 2025-10-07 17:16 disk.ovf
-rw-r--r-- root/root       167 2025-10-07 17:16 disk.mf
-rw-r--r-- root/root 1236157952 2025-10-07 17:16 disk.vmdk

[bcl]

Looks good!

[supakeen]

Not really requesting changes but I do want to clear this up. Is there a reason that we're using .tar as the extension here while we use .ova (which is a tar) for other ova-imagetypes?

Do any of the places where ova's get used expect a certain suffix?

[mvo5]

Not really requesting changes but I do want to clear this up. Is there a reason that we're using .tar as the extension here while we use .ova (which is a tar) for other ova-imagetypes?

Do any of the places where ova's get used expect a certain suffix?

Thanks for noticing! We had this name hardcoded in bib and I did not double check with the other image types - I agree, lets make it consistent, especially if there is image.ova since forever everywhere. Unfortuantely I had to tweak one or two more things to be able to make this change but it should be good now (and I added a test which is also more verbose than I would like, I will try to go into manifesttest again and see if we can improve this but that is for another PR :)