[llvm] [BOLT][DWARF] Cleanup buffer initialization for DWO range writer (PR #97843)

[Alexander Yermolovich via llvm-commits]

ayermolo wrote:

OK for this one better approach add
/// Inits Ranges section with empty list.
  void initSection();
  
Move 
SectionOffset +=
      writeAddressRanges(*RangesStream.get(), DebugAddressRangesVector{});
 from constructor to implementation.
 
 LegacyRangesSectionWriterByCU->initSection(CU); is not necessary
 
 then call
 LegacyRangesSectionWriter->initSection();
 Drop the new test. I'll check it in as part of my PR  

https://github.com/llvm/llvm-project/pull/97843