Fix mislabeled tag in pulp-web publish & simplify compose testing to only pulp-minimal images

[gerrod3]

Despite what the code says we actually can only build amd64 images for pulp-web, since its base image only has amd64 variants. With the update to Ubuntu 24 in the workers we got a new podman version. I think this new version fixed a bug/behavior we were using in the publish step and thus we no longer publish two tags for the pulp-web single amd64 image. It now seems to just choose the last tag in the list as the sole tag to push, so hopefully switching the order should fix it temporarily. We'll need to do some work to get proper arm64 images built for pulp-web.

Also, I simplified the compose tests to only occur when we built the pulp-minimal/web images. This reduces the amount of cross dependency between the different image scenario testing.

[patchback]

Backport to 3.49: 💔 cherry-picking failed — conflicts found

❌ Failed to cleanly apply 801dc23 on top of patchback/backports/3.49/801dc23b39c67313d8ce632379c2b90270bc69ce/pr-680

Backporting merged PR #680 into latest

1. Ensure you have a local repo clone of your fork. Unless you cloned it
   from the upstream, this would be your origin remote.
2. Make sure you have an upstream repo added as a remote too. In these
   instructions you'll refer to it by the name upstream. If you don't
   have it, here's how you can add it:

   $ git remote add upstream https://github.com/pulp/pulp-oci-images.git

3. Ensure you have the latest copy of upstream and prepare a branch
   that will hold the backported code:

   $ git fetch upstream
   $ git checkout -b patchback/backports/3.49/801dc23b39c67313d8ce632379c2b90270bc69ce/pr-680 upstream/3.49

4. Now, cherry-pick PR Fix mislabeled tag in pulp-web publish & simplify compose testing to only pulp-minimal images #680 contents into that branch:

   $ git cherry-pick -x 801dc23b39c67313d8ce632379c2b90270bc69ce

   If it'll yell at you with something like fatal: Commit 801dc23b39c67313d8ce632379c2b90270bc69ce is a merge but no -m option was given., add -m 1 as follows instead:

   $ git cherry-pick -m1 -x 801dc23b39c67313d8ce632379c2b90270bc69ce

5. At this point, you'll probably encounter some merge conflicts. You must
   resolve them in to preserve the patch from PR Fix mislabeled tag in pulp-web publish & simplify compose testing to only pulp-minimal images #680 as close to the
   original as possible.
6. Push this branch to your fork on GitHub:

   $ git push origin patchback/backports/3.49/801dc23b39c67313d8ce632379c2b90270bc69ce/pr-680

7. Create a PR, ensure that the CI is green. If it's not — update it so that
   the tests and any other checks pass. This is it!
   Now relax and wait for the maintainers to process your pull request
   when they have some cycles to do reviews. Don't worry — they'll tell you if
   any improvements are necessary when the time comes!

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