libutils: RefBase DEBUG_REF love

Done here:
- path saved to a useable location on host
- path always printed (for visibility for new users)
- open(.., 666) - That's '01204' not '0644' oops

Future considerations:
- make defines constexpr instead of ifdef
- copy malloc hook design to avoid needing to recompile code
- make libutilscallstack default on host
- run libutils tests, not just test compile debug mode
- code incorrectly prints ref 'doesn't exist'
  seems it's gotten out of sync, but still good enough
  to use stacktraces

Bug: 244325464
Test: manual
Change-Id: I732e5b8aec3cd946ef3559a2a814caf693846cc0