Image Customizer: Multiple kernels problems

In the Azure Linux tdnf config, there is the following:

[main]
...
installonly_limit=3
installonlypkgs=kernel kernel-mshv kernel-uvm kernel-uki kernel-64k
...

The allows for there to be multiple kernel package versions installed at the same time.

Having backup kernels is useful for systems that do package updates since a new kernel version might be faulty/problematic. But for building images, most people don't want multiple kernels installed.

This typically shows up when a user installs a package that depends on a specific version of the kernel package. For example, kernel-drivers-gpu or kernel-tools. When such a package is installed and a newer version of the kernel is available, this triggers the installation of a second kernel in the image.

The current recommendation for users is to do the following in their config:

os:
  packages:
    remove:
    - kernel

    install:
    - kernel
    - kernel-tools

Since, 'remove' happens before 'install' and 'remove' will remove all versions of a package, this results in only a single kernel being installed in the image.

However, we should investigate ways to improve the user experience.

Start by reproducing the multiple-kernel behavior using the shown tdnf settings and the os.packages remove/install configuration. Trace how Image Customizer processes package removal and installation, then define and validate a user-friendly behavior that avoids unintended kernel versions while preserving explicit package requests.