Deprecate and rename `Layer.render`

`Layer#render` is called to refresh a layer's internal canvas. The term "render" could imply the rendering of a visual frame or an audio sample. Renaming it to something like `draw` would remove this ambiguity. We will later add a similar method that will be used to render an audio sample. The task here is to deprecate `Layer.render()` and add an identical method with a different name.