vars_files, include_vars don't work with role vars

I want to separate vars in a role structure from vars/main.yml into different files using vars_files or include_vars as per Variable File Separation, with something like

`

The vars/main.yml cannot contain keywords, it (like all vars files)
MUST be a dictionary, not a list.

There is no way to do 'includes' inside a vars file. What you are
doing is just not supported.

Since you triaged #32328, could you turn it into a feature request? Role vars separation would be a useful addition.