Implement WRY interface on top of off-screen rendering samples

[wravery]

We probably don't want to add this directly to WRY, since that's focused on hosting system webviews, but if we can implement a drop-in replacement that re-exports the same public interfaces as WRY, then we should be able to integrate this more easily into the rest of the Tauri runtime/framework.

This will likely require multiple sub-issues itself, possibly broken up into a few per-platform.

[csmoe]

https://github.com/tauri-apps/wry/blob/48e5e9903fbc14ba8ad10b4e2fffae29b10d3d86/src/webview2/mod.rs#L108
I used to think tauri will draw the webcontent along with some custom native views, turns out the whole window is just a webview. Given how wry create the webview nowadays, off-screen seems not needed, just mount tao/winit window's handle to cef browser's window_info.parent(this works since I tried locally before implementing osr).

off-screen is a viable approach, but it requires efforts to redirect i/o event like mouse/keybord and embed wgpu to tauri, osr is more fittable for native ui frameworks like iced, slint.

[wravery]

Interesting... yeah, that makes sense. We could get this working in Tauri a lot faster if we can leverage the windowed CEF view. For maximum compatibility with the Tauri runtime, we might need another tracking item to implement TAO/winit adapters for the CEF-native window management.