[api] Fix handle leak when getting Context embedder data

The `Context::SlowGetAlignedPointerFromEmbedderData()` method returns
a pointer, so the fact that it allocates handles is not obvious to
the caller.

Since this is the slow path anyway, simply add a handle scope inside
of it.

The tests are also modified to perform the same check for the
`Object` equivalent of this method.

Change-Id: I5f03c9a7b70b3a17315609df021606a53c9feb2d
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1879902Reviewed-by: Yang Guo <yangguo@chromium.org>
Commit-Queue: Yang Guo <yangguo@chromium.org>
Cr-Commit-Position: refs/heads/master@{#64583}

src/api/api.cc

@@ -1312,6 +1312,7 @@ void Context::SetEmbedderData(int index, v8::Local<Value> value) {
 
 void* Context::SlowGetAlignedPointerFromEmbedderData(int index) {
   const char* location = "v8::Context::GetAlignedPointerFromEmbedderData()";
+  HandleScope handle_scope(GetIsolate());
   i::Handle<i::EmbedderDataArray> data =
       EmbedderDataFor(this, index, false, location);
   if (data.is_null()) return nullptr;

test/cctest/test-api.cc

@@ -2956,8 +2956,11 @@ THREADED_TEST(SetAlignedPointerInInternalFields) {
 
   obj->SetAlignedPointerInInternalFields(2, indices, values);
   CcTest::CollectAllGarbage();
+  {
+    v8::SealHandleScope no_handle_leak(isolate);
     CHECK_EQ(heap_allocated_1, obj->GetAlignedPointerFromInternalField(0));
     CHECK_EQ(heap_allocated_2, obj->GetAlignedPointerFromInternalField(1));
+  }
 
   indices[0] = 1;
   indices[1] = 0;
@@ -3010,6 +3013,7 @@ THREADED_TEST(EmbedderDataAlignedPointers) {
   }
   CcTest::CollectAllGarbage();
   for (int i = 0; i < 100; i++) {
+    v8::SealHandleScope no_handle_leak(env->GetIsolate());
     CHECK_EQ(AlignedTestPointer(i), env->GetAlignedPointerFromEmbedderData(i));
   }
 }