[DebugInfo][llvm-dwarfutil] Combine overlapped address ranges.

DWARF files may contain overlapping address ranges. f.e. it can happen if the two
copies of the function have identical instruction sequences and they end up sharing.
That looks incorrect from the point of view of DWARF spec. Current implementation
of DWARFLinker does not combine overlapped address ranges. It would be good if such
ranges would be handled in some useful way. Thus, this patch allows DWARFLinker
to combine overlapped ranges in a single one.

Depends on D86539

Reviewed By: aprantl

Differential Revision: https://reviews.llvm.org/D123469