Extend the Texture asset type to support 3D data
Textures are still loaded from images as 2D, but they can be reshaped
according to how the render pipeline would like to use them.
Also add an example of how this can be used with the texture2DArray uniform type.
* Remove cfg!(feature = "metal-auto-capture")
This cfg! has existed since the initial commit, but the corresponding
feature has never been part of Cargo.toml
* Remove unnecessary handle_create_window_events call
* Remove EventLoopProxyPtr wrapper
* Remove unnecessary statics
* Fix unrelated deprecation warning to fix CI
