Utility module to retrieve fields of structs of classes

`type field_type``= InferIR.Typ.Fieldname.t * InferIR.Typ.t * (InferIR.Annot.t * bool) list```
`val get_fields : CAst_utils.qual_type_to_sil_type ‑> InferIR.Tenv.t ‑> InferIR.Typ.Name.t ‑> InferGenerated.Clang_ast_t.decl list ‑> field_type list`
`val fields_superclass : InferIR.Tenv.t ‑> InferGenerated.Clang_ast_t.obj_c_interface_decl_info ‑> field_type list`
`val add_missing_fields : InferIR.Tenv.t ‑> InferIR.QualifiedCppName.t ‑> field_type list ‑> unit`
`val modelled_field : InferGenerated.Clang_ast_t.named_decl_info ‑> field_type list`