Solari: Fix normal maps and support two-channel maps

[JMS55]

I was missing the * 2.0 - 1.0 before. See:

bevy/crates/bevy_pbr/src/render/pbr_functions.wgsl

Lines 204 to 210 in 0eac08a

	if (standard_material_flags & pbr_types::STANDARD_MATERIAL_FLAGS_TWO_COMPONENT_NORMAL_MAP) != 0u {
	// Only use the xy components and derive z for 2-component normal maps.
	Nt = vec3<f32>(Nt.rg * 2.0 - 1.0, 0.0);
	Nt.z = sqrt(1.0 - Nt.x * Nt.x - Nt.y * Nt.y);
	} else {
	Nt = Nt * 2.0 - 1.0;
	}

Also now we reconstruct Z so that two-channel normal maps (e.g. from the texture compressor plugin) are supported.