[llvm] [BOLT][DWARF] Refactor legacy ranges writers (PR #96006)

[Maksim Panchenko via llvm-commits]

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@@ -89,6 +89,15 @@ class DWARFRewriter {
   /// Store Rangelists writer for each DWO CU.
   RangeListsDWOWriers RangeListsWritersByCU;
 
+  /// Contains ranges writer and die.
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maksfb wrote:

Briefly describe what this datatype is used for. The reader could see the contents in the lines below.

https://github.com/llvm/llvm-project/pull/96006