Cleaner resolution for the problem mentioned last commit.
Fixes mono-namespace charts while assuming multi-namespace charts
have the diligence to set `.metadata.namespace` everywhere necessary.
It doesn't make sense for `kubeVersions` to be an _input_ to the module,
i.e., one provided by the Haumea loader. Let it be passed inside the
foldler instead, like `apiVersions`.
En passant, I realized it's as easy to expose apiVersions to user input;
maybe one'd want to specify APIs not installed by this flake.
