[NFC] Make unwind table internal data structures more accessible (#145804)

All these changes are being used in
[PR#145633](https://github.com/llvm/llvm-project/pull/145633)

`CFIProgram`:
- `addInstruction` methods already exists, but more convenient ones are
private, this PR makes them public

`UnwindLocation`:
- Added a field accessor method for `Dereference` like other field
access methods.

llvm/include/llvm/DebugInfo/DWARF/DWARFDebugFrame.h

@@ -138,6 +138,8 @@ public:
     return *AddrSpace;
   }
   int32_t getConstant() const { return Offset; }
+  bool getDereference() const { return Dereference; }
+
   /// Some opcodes will modify the CFA location's register only, so we need
   /// to be able to modify the CFA register when evaluating DWARF Call Frame
   /// Information opcodes.

llvm/include/llvm/DebugInfo/DWARF/LowLevel/DWARFCFIProgram.h

@@ -254,12 +254,6 @@ public:
   /// above. This is indexed by opcode.
   LLVM_ABI static ArrayRef<OperandType[MaxOperands]> getOperandTypes();
 
-private:
-  std::vector<Instruction> Instructions;
-  const uint64_t CodeAlignmentFactor;
-  const int64_t DataAlignmentFactor;
-  Triple::ArchType Arch;
-
   /// Convenience method to add a new instruction with the given opcode.
   void addInstruction(uint8_t Opcode) {
     Instructions.push_back(Instruction(Opcode));
@@ -286,6 +280,12 @@ private:
     Instructions.back().Ops.push_back(Operand2);
     Instructions.back().Ops.push_back(Operand3);
   }
+
+private:
+  std::vector<Instruction> Instructions;
+  const uint64_t CodeAlignmentFactor;
+  const int64_t DataAlignmentFactor;
+  Triple::ArchType Arch;
 };
 
 } // end namespace dwarf