UI components not respecting RenderLayers

The visibility of UI entities like text is not affected by the `RenderLayers` component. This is a problem when trying to prerender a scene with `RenderTarget::Image` to use it as a mesh texture (the game UI will also be visible on the texture).

Is there a way to make UI components respect `RenderLayers`?

The issue concerns UI entities such as text, the RenderLayers component, and RenderTarget::Image scene prerendering. Start by tracing how UI visibility is handled during image rendering; done means UI components respect RenderLayers so unrelated game UI is excluded from a mesh texture, with coverage for that use case.

Written by the indexing model from the issue text.