Revert of [turbofan] inline %StringIteratorPrototype%.next in JSBuiltinReducer.

src/code-stub-assembler.h

Index: src/code-stub-assembler.h
diff --git a/src/code-stub-assembler.h b/src/code-stub-assembler.h
index 6dc677f5b825bcd8fe2b78c27f39c43267f69ef9..524371978f77d9b69518bc0e154983e9f19368a6 100644
--- a/src/code-stub-assembler.h
+++ b/src/code-stub-assembler.h
@@ -18,6 +18,12 @@
 class StubCache;
 
 enum class PrimitiveType { kBoolean, kNumber, kString, kSymbol };
+
+enum class UnicodeEncoding {
+  // Different unicode encodings in a |word32|:
+  UTF16,  // hi 16bits -> trailing surrogate or 0, low 16bits -> lead surrogate
+  UTF32,  // full UTF32 code unit / Unicode codepoint
+};
 
 #define HEAP_CONSTANT_LIST(V)                 \
   V(BooleanMap, BooleanMap)                   \