[DWARF] Fix DWARFVerifier::DieRangeInfo::contains

It didn't handle empty LHS correctly. If two ranges of LHS were
contiguous and jointly contained one range of RHS, it could also be incorrect.

DWARFAddressRange::contains can be removed and its tests can be merged into DWARFVerifier::DieRangeInfo::contains

llvm-svn: 358387