What package is installed as provided from possibilities is decided alphabetically
If we have more than one possible provided candidate for package then we decide
which one we use simply alphabetically by their name. This makes decision stable
but gives us no free hands and only way how to change that is to add Install
command but that has side effect that it won't be removed as soon as other
provided candidate is selected. Solution would be to add possibility for packages
to specify their own preference (Package("pkg", {prefer={"apkg", "bpkg"}})
.