fix prepass normal_mapping

[robtfm]

Objective

#5703 caused the normal prepass to fail as the prepass uses pbr_functions::apply_normal_mapping, which uses mesh_view_bindings::view to determine mip bias, which conflicts with prepass_bindings::view.

Solution

pass the mip bias to the apply_normal_mapping function explicitly.

[superdump]

Looks straight forward enough to me.

[cart]

A reasonable fix for now. Ideally we find a way to prevent these clashes across files. We (and our users) will likely continue to hit this.

[robtfm]

Ideally we find a way to prevent these clashes across files

I think the best fix for this is to move the binding into the bevy_render::view file alongside the struct. then you can't import the view struct/variable without also importing the binding, and all references to the binding will be the same. prepass would import it, main pass would import it as well, both could then refer to it freely. generally any functions that need the view could import it freely without clashes.

it would mean that the view struct absolutely cannot be used in a slot other than slot 0, without explicitly copy/pasting the struct definition. i think that's fine (and with automatic group 0 it would be irrelevant anyway).

it is quite invasive though so i will leave it till after the release. it should also be done for globals, mesh bindings, etc.