[turbofan] Introduce an ExternalPointer type.

src/compiler/access-builder.cc

Index: src/compiler/access-builder.cc
diff --git a/src/compiler/access-builder.cc b/src/compiler/access-builder.cc
index 1ca63dfdbbd1f40476e87357a0be0a77cb3fc471..982043bac234cbc7f83a81419d3f7cb1903ec8f1 100644
--- a/src/compiler/access-builder.cc
+++ b/src/compiler/access-builder.cc
@@ -357,7 +357,7 @@ FieldAccess AccessBuilder::ForFixedTypedArrayBaseExternalPointer() {
   FieldAccess access = {kTaggedBase,
                         FixedTypedArrayBase::kExternalPointerOffset,
                         MaybeHandle<Name>(),
-                        Type::OtherInternal(),
+                        Type::ExternalPointer(),
                         MachineType::Pointer(),
                         kNoWriteBarrier};
   return access;
@@ -512,7 +512,7 @@ FieldAccess AccessBuilder::ForExternalStringResourceData() {
   FieldAccess access = {kTaggedBase,
                         ExternalString::kResourceDataOffset,
                         Handle<Name>(),
-                        Type::OtherInternal(),
+                        Type::ExternalPointer(),
                         MachineType::Pointer(),
                         kNoWriteBarrier};
   return access;