[Interpreter]: Add kRegList operand type for register list operands.

src/interpreter/bytecode-register.cc

Index: src/interpreter/bytecode-register.cc
diff --git a/src/interpreter/bytecode-register.cc b/src/interpreter/bytecode-register.cc
index 31e3b908527e229278684e70465b128b01881626..1ce512b0e062fc9f7717e6536c5bb2dc0c1d0483 100644
--- a/src/interpreter/bytecode-register.cc
+++ b/src/interpreter/bytecode-register.cc
@@ -121,7 +121,7 @@ bool Register::AreContiguous(Register reg1, Register reg2, Register reg3,
   return true;
 }
 
-std::string Register::ToString(int parameter_count) {
+std::string Register::ToString(int parameter_count) const {
   if (is_current_context()) {
     return std::string("<context>");
   } else if (is_function_closure()) {