Add runtime detection of V8 memory cage #3384

When using the V8 memory cage, Buffers cannot be wrapped and then
later freed via a callback. When the cage is detected via a throw,
instead fall back to copying Buffer contents to V8 memory.

This approach will be used by Electron 21+ and you should expect
reduced performance and increased memory consumption/fragmentation.

src/common.h

@@ -133,6 +133,7 @@ namespace sharp {
     return static_cast<T>(
       vips_enum_from_nick(nullptr, type, AttrAsStr(obj, attr).data()));
   }
+  Napi::Buffer<char> NewOrCopyBuffer(Napi::Env env, char* data, size_t len);
 
   // Create an InputDescriptor instance from a Napi::Object describing an input image
   InputDescriptor* CreateInputDescriptor(Napi::Object input);