[BOLT][DWARF] Fix parent chain in debug_names entries with forward declaration. (#93865)

Previously when an entry was skipped in parent chain a child will point
to the next valid entry in the chain. After discussion in
https://github.com/llvm/llvm-project/pull/91808 this is not very useful.
Changed implemenation so that all the children of the entry that is
skipped won't have DW_IDX_parent.