cxx-qt-lib bindings for QSGNode and subclasses

[Be-ing]

to enable users to implement GPU rendered custom QQuickItems in Rust

[ahayzen-kdab]

This would likely be for custom QQuickItem's. We would also need to consider the benefit, as the current benefit of cxx-qt-lib is that we handle making the Qt types trivial where they are relocatable (which CXX doesn't understand). Whereas i believe these types are all pointer driven so can be implemented in CXX natively.

But it does remove boilerplate.

So likely these would be under a quick opt-in ( ? ) feature for cxx-qt-lib to help remove boilerplate.

[Be-ing]

The benefit would be saving downstream users from having to make these bindings.

So likely these would be under a quick opt-in ( ? ) feature for cxx-qt-lib to help remove boilerplate.

sure