also removes `logical_width` & `logical_height` as they are not longer different

* values in the `WindowDescriptor` and the `set_resolution` call are now "requested" sizes
* once the window is created, the actual width and height are learned along with the scale factor
* `width` and `height` return the actual size or the requested size if the window has not been created yet
* add some documentation for the window size APIs
* update a handfull of examples to change the window size of f32