The `require_wgpu_24` function accepts either a fully setup WGPU, or one
can configure individual aspects such as features/limits.
The wgpu_texture example uses this to add push constants to the required
features and thus eliminates the need for uniform buffers.
This adds a `unstable-wgpu-24` feature that exposes WGPU types in the
GraphicsAPI enum, adds `require_wgpu_24()` to the backend selector,
and adds a conversion from `wgpu::Texture` to `slint::Image`.
The `require_wgpu_24()` function in the selector will be extended in the
future (before the next release) to permit specifying additional aspects
of the WGPU configuration.
Co-Authored-By: Olivier Goffart <olivier.goffart@slint.dev>
