Reland "[sandbox] Sandboxify ExternalString external pointers"

This is a reland of commit e7bf8110

Shared string GC issues have been fixed in https://crrev.com/c/3875028

Original change's description:
> [sandbox] Sandboxify ExternalString external pointers
>
> Bug: v8:10391
> Change-Id: I0f737e5adf6e4fd24f93436fa5680ff20c1536da
> Cq-Include-Trybots: luci.v8.try:v8_linux64_heap_sandbox_dbg_ng,v8_linux_arm64_sim_heap_sandbox_dbg_ng
> Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3757901
> Commit-Queue: Samuel Groß <saelo@chromium.org>
> Reviewed-by: Igor Sheludko <ishell@chromium.org>
> Reviewed-by: Leszek Swirski <leszeks@chromium.org>
> Cr-Commit-Position: refs/heads/main@{#82958}

Bug: v8:10391
Change-Id: I555498973dc9d5dcc4163b3b1258e41d7148e2d5
Cq-Include-Trybots: luci.v8.try:v8_linux64_heap_sandbox_dbg_ng,v8_linux_arm64_sim_heap_sandbox_dbg_ng
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3872273Reviewed-by: Leszek Swirski <leszeks@chromium.org>
Reviewed-by: Igor Sheludko <ishell@chromium.org>
Commit-Queue: Samuel Groß <saelo@chromium.org>
Cr-Commit-Position: refs/heads/main@{#83026}

include/v8-internal.h

@@ -373,8 +373,8 @@ constexpr uint64_t kAllExternalPointerTypeTags[] = {
 #define SHARED_EXTERNAL_POINTER_TAGS(V)                        \
   V(kFirstSharedTag,                        sandboxed, TAG(0)) \
   V(kWaiterQueueNodeTag,                    sandboxed, TAG(0)) \
-  V(kExternalStringResourceTag,           unsandboxed, TAG(1)) \
-  V(kExternalStringResourceDataTag,       unsandboxed, TAG(2)) \
+  V(kExternalStringResourceTag,             sandboxed, TAG(1)) \
+  V(kExternalStringResourceDataTag,         sandboxed, TAG(2)) \
   V(kLastSharedTag,                         sandboxed, TAG(2))
 
 // External pointers using these tags are kept in a per-Isolate external

src/snapshot/serializer.cc

@@ -595,13 +595,13 @@ void Serializer::ObjectSerializer::SerializeExternalString() {
   if (serializer_->external_reference_encoder_.TryEncode(resource).To(
           &reference)) {
     DCHECK(reference.is_from_api());
-#ifdef V8_SANDBOXED_EXTERNAL_POINTERS
+#ifdef V8_ENABLE_SANDBOX
     uint32_t external_pointer_entry =
         string->GetResourceRefForDeserialization();
 #endif
     string->SetResourceRefForSerialization(reference.index());
     SerializeObject();
-#ifdef V8_SANDBOXED_EXTERNAL_POINTERS
+#ifdef V8_ENABLE_SANDBOX
     string->SetResourceRefForSerialization(external_pointer_entry);
 #else
     string->set_address_as_resource(isolate(), resource);

tools/debug_helper/get-object-properties.cc

@@ -349,7 +349,7 @@ class ReadStringVisitor : public TqObjectVisitor {
     if (IsExternalStringCached(object)) {
       ExternalPointer_t resource_data =
           GetOrFinish(object->GetResourceDataValue(accessor_));
-#ifdef V8_SANDBOXED_EXTERNAL_POINTERS
+#ifdef V8_ENABLE_SANDBOX
       Isolate* isolate = GetIsolateForSandbox(
           HeapObject::unchecked_cast(Object(heap_addresses_.any_heap_pointer)));
       ExternalPointerHandle handle =
@@ -359,7 +359,7 @@ class ReadStringVisitor : public TqObjectVisitor {
               handle, kExternalStringResourceDataTag));
 #else
       uintptr_t data_address = static_cast<uintptr_t>(resource_data);
-#endif  // V8_COMPRESS_POINTERS
+#endif  // V8_ENABLE_SANDBOX
       if (done_) return;
       ReadStringCharacters<TChar>(object, data_address);
     } else {