Prior to this commit, `v8::NamedPropertyHandlerConfiguration`
and `v8::IndexedPropertyHandlerConfiguration` did not expose the
`definer` hook, or `flags`.
This commit adds these options. In the process of doing this a couple of
other changes were made:
- Bitflag enum consts are now member consts of the related struct.
This is done because PropertyHandlerFlags has conflicts with
PropertyAttribute.
- PropertyDescriptor gets all C++ introspection methods exposed to Rust.
- NamedPropertyHandlerConfiguration callback types get rustdoc comments.
- IndexedPropertyHandlerConfiguration callback types get rustdoc
comments.
- GenericNamedPropertySetterCallback gets a ReturnValue parameter, to
signal trap passthrough.
Co-authored-by: Bartek Iwańczuk <biwanczuk@gmail.com>
