fix: avoid circular references to complex attribute types

[radeksimko]

Parsing the following config would lead to the creation of circular references, which then cause a loop while copying the references in LS:

locals {
  top_obj = {
    first = {
      attr = "val"
    }
    second = {
      attr = "val"
    }
    third = {
      attr = "val"
    }
    fourth = {
      attr = "val"
    }
  }
}