[debuginfo] Don't return an error when it isn't possible to resolve a name

[calixteman]

Some functions are skipped because an error is returned when trying to resolve a function name using a reference.
I met some case where the references (via abstract_origin) are wrong (they don't point to a DIE).
If such a function is an inlinee then the inliner is skipped which is pretty bad.
I think that in such a case the resolve_function_name should return something like <name omitted>, it's probably better to have an incomplete information instead of removing the inliner.
We could do the same for resolve_file.