[BOLT][NFC] Make DWOId std::optional

bolt/include/bolt/Core/DebugData.h

class DebugAbbrevWriter {
   using AbbrevEntryTy = std::unordered_map<const DWARFAbbreviationDeclaration *,
                                            SmallVector<AbbrevEntry, 2>>;
   std::unordered_map<const DWARFUnit *, AbbrevEntryTy> NewAbbrevEntries;
 
   /// DWARF context containing abbreviations.
   DWARFContext &Context;
 
   /// DWO ID used to identify unit contribution in DWP.
-  Optional<uint64_t> DWOId;
+  std::optional<uint64_t> DWOId;
 
   /// Add abbreviations from compile/type \p Unit to the writer.
   void addUnitAbbreviations(DWARFUnit &Unit);
 
 public:
   /// Create an abbrev section writer for abbreviations in \p Context.
   /// If no \p DWOId is given, all normal (non-DWO) abbreviations in the
   /// \p Context are handled. Otherwise, only abbreviations associated with
   /// the compile unit matching \p DWOId in DWP or DWO will be covered by
   /// an instance of this class.
   ///
   /// NOTE: Type unit abbreviations are not handled separately for DWOs.
   ///       Most of the time, using type units with DWO is not a good idea.
   ///       If type units are used, the caller is responsible for verifying
   ///       that abbreviations are shared by CU and TUs.
   DebugAbbrevWriter(DWARFContext &Context,
-                    Optional<uint64_t> DWOId = std::nullopt)
+                    std::optional<uint64_t> DWOId = std::nullopt)
       : Context(Context), DWOId(DWOId) {}
 
   DebugAbbrevWriter(const DebugAbbrevWriter &) = delete;
   DebugAbbrevWriter &operator=(const DebugAbbrevWriter &) = delete;
 
   DebugAbbrevWriter(DebugAbbrevWriter &&) = delete;
   DebugAbbrevWriter &operator=(DebugAbbrevWriter &&) = delete;