[lldb/DWARF] Bypass the compres^Wconstruction of DIERefs in debug_names (#93296)

DebugNamesDWARFIndex was jumping through hoops to construct a DIERef
from an index entry only to jump through them back a short while later
to construct a DWARFDIE.

This used to be necessary as the index lookup was a two stage process,
where we first enumerated all matches, and then examined them (so it was
important that the enumeration was cheap -- does not trigger unnecessary
parsing). However, now that the processing is callback based, we are
always immediately examining the DWARFDIE right after finding the entry,
and the DIERef just gets in the way.