[libc++][TZDB] Fixes reverse time lookups. (#89502)

Testing with the get_info() returning a local_info revealed some issues
in the reverse lookup. This needed an additional quirk. Also the
skipping when not in the current continuation optimization was wrong. It
prevented merging two sys_info objects.

GitOrigin-RevId: 4e9decf294a19d0047da3aada980f24d19d6c62c
2 files changed