Add method to get an array of modules included in a type

[Blacksmoke16]

This would be the inverse of #8133. Where given a TypeNode, call a method to get an array of modules included in that type. E.g.

module Bar
end

struct Foo
  include Bar
end

# Or maybe `.included_modules` to be more explicit?
{{Foo.included}} # => [Bar] 

EDIT: Or maybe just also use #includers, but have it function based on if it is used on a module vs class/struct TypeNode.

This is currently already possible, but this would just provide a better API compared to:

{{pp Foo.ancestors.select &.module?}}