Fix AmbientLight::affects_lightmapped_meshes not working

[marlyx]

Objective

Fix lightmapped materials not respecting the AmbientLight::affects_lightmapped_meshes setting.

NOTE: This only makes the setting work on the forward renderer. Making it work on the deferred renderer would probably require encoding more information in the g-buffer or similar. Please advise if I missed some obvious way to get it working on deferred.

Solution

• Make ambient light conditionally applied depending on the affects_lightmapped_meshes setting when material mesh i lightmapped
• Remove what looks to be leftover Lights (wgsl) members: environment_map_smallest_specular_mip_level, environment_map_intensity. (These where not present in the rust equivalent GpuLights and was not used in the wgsl code)

Open Questions

• Ambient light is also blended into the transmitted light if DIFFUSE_TRANSMISSION is enabled on the material. Should that also be guarded by the same conditional as the indirect contribution?

Testing

Ran a modified version of the lightmaps example, where there is a bright red ambient light added and the small cube do not have a lightmap added (To be able to see ambient light applied to meshes without lightmaps)

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Showcase

Main: Lightmap example with bright red ambient, small box have no lightmap

(All meshes get ambient light even when affects_lightmapped_meshes = false)

This PR: Lightmap example with bright red ambient, small box have no lightmap

(Only the small box get ambient light when affects_lightmapped_meshes = false)

[janhohenheim]

No comment about the dead code removed, but the disabled ambient light looks sound to me :)