Introduce a base pointer field in FixedTypedArrayBase and teach GC about it

src/hydrogen-instructions.h

Index: src/hydrogen-instructions.h
diff --git a/src/hydrogen-instructions.h b/src/hydrogen-instructions.h
index 9d48a22333b923959b9d7483598008793f881cbe..15aa385851db47b46233de986c0a7afc9d5c4b42 100644
--- a/src/hydrogen-instructions.h
+++ b/src/hydrogen-instructions.h
@@ -5928,6 +5928,11 @@ class HObjectAccess final {
         Representation::Smi());
   }
 
+  static HObjectAccess ForFixedTypedArrayBaseBasePointer() {
+    return HObjectAccess(kInobject, FixedTypedArrayBase::kBasePointerOffset,
+                         Representation::Tagged());
+  }
+
   static HObjectAccess ForStringHashField() {
     return HObjectAccess(kInobject,
                          String::kHashFieldOffset,