Extend `counted_by` support beyond struct fields

Currently, `counted_by` and related attributes are only supported in struct fields. This issue tracks extending support to:

- Function parameters
- Return types
- Global variables
- Local variables

For `typedef`, support would only make sense if the attribute argument is a constexpr or constant literal.

Start by tracing the existing counted_by and related-attribute support for struct fields. Then examine how function parameters, return types, global variables, local variables, and typedefs are represented; done means support covers the listed declaration kinds while typedef arguments remain limited to constexpr or constant literals.

Written by the indexing model from the issue text.