[turbofan] Use CompareNilIC for abstract equality with null/undefined.

src/code-factory.h

Index: src/code-factory.h
diff --git a/src/code-factory.h b/src/code-factory.h
index 1821b0d8f537e47b9fee7c261c8187492e30a258..2b0dfed0ca75e8009b18c6e5228d690e72befa26 100644
--- a/src/code-factory.h
+++ b/src/code-factory.h
@@ -56,6 +56,7 @@ class CodeFactory final {
 
   static Callable CompareIC(Isolate* isolate, Token::Value op,
                             Strength strength);
+  static Callable CompareNilIC(Isolate* isolate, NilValue nil_value);
 
   static Callable BinaryOpIC(Isolate* isolate, Token::Value op,
                              Strength strength);