Improvement to layer handling by render passes

[mvaligursky]

related to #6949

• When a RenderPassCamera creates forward render passes, it includes even disabled layers, and the layers can be later toggled on and off as needed
• When a layer from the composition is deleted, a warning is printed and the layer is ignored if still included in forward passes. Those need to be re-created to avoid this.
• when PostEffects are used on the same camera as render passes, a warning is logged and post-effects are skipped, as this is not compatible