[DWARF] Add accessor for NameIndex Offsets field. (#88783)

Add an accessor function to DWARFDebugNames::NameIndex to allow other
classes to access the Offsets field within NameIndex. This will be used
by LLD to create a merged .debug_names index
(#86508)

Author: cmtice

llvm/include/llvm/DebugInfo/DWARF/DWARFAcceleratorTable.h

@@ -608,6 +608,9 @@ class DWARFDebugNames : public DWARFAcceleratorTable {
     /// Returns Hdr field
     Header getHeader() const { return Hdr; }
 
+    /// Returns Offsets field
+    DWARFDebugNamesOffsets getOffsets() const { return Offsets; }
+
     /// Reads offset of compilation unit CU. CU is 0-based.
     uint64_t getCUOffset(uint32_t CU) const;
     uint32_t getCUCount() const { return Hdr.CompUnitCount; }