Add a new debugging / development tool `osbuild-package-sets` for
printing JSON object with all package sets of a specific distro x arch x
image type combination.
This is useful, since due to the way package sets are implemented in
composer, the actual package set of a vanilla image type is very
difficult to determine just by looking at the code.
Example usage:
`go run cmd/osbuild-package-sets/main.go -distro rhel-90 -arch x86_64
-image qcow2`
