MIPS: Reland of `Fix bad RegisterConfiguration usage in InstructionSequence unit tests`

src/compiler/instruction.h

Index: src/compiler/instruction.h
diff --git a/src/compiler/instruction.h b/src/compiler/instruction.h
index 872d664f258cab7a489fb3c16f0d5f2696dec99f..e63ceda14846cf1ecd65c44eb41a7f9247b04b94 100644
--- a/src/compiler/instruction.h
+++ b/src/compiler/instruction.h
@@ -1570,12 +1570,19 @@ class V8_EXPORT_PRIVATE InstructionSequence final
   void ValidateDeferredBlockEntryPaths() const;
   void ValidateSSA() const;
 
+  static void SetRegisterConfigurationForTesting(
+      const RegisterConfiguration* regConfig);
+  static void ClearRegisterConfigurationForTesting();
+
  private:
   friend V8_EXPORT_PRIVATE std::ostream& operator<<(
       std::ostream& os, const PrintableInstructionSequence& code);
 
   typedef ZoneMap<const Instruction*, SourcePosition> SourcePositionMap;
 
+  static const RegisterConfiguration* RegisterConfigurationForTesting();
+  static const RegisterConfiguration* registerConfigurationForTesting_;
+
   Isolate* isolate_;
   Zone* const zone_;
   InstructionBlocks* const instruction_blocks_;