fix orthographic cluster aabb for spotlight culling (#9614)

# Objective

fix #9605

spotlight culling uses an incorrect cluster aabb for orthographic
projections: it does not take into account the near and far cluster
bounds at all.

## Solution

use z_near and z_far to determine cluster aabb in orthographic mode.

i'm not 100% sure this is the only change that's needed, but i am sure
this change is needed, and the example seems to work well now
(CLUSTERED_FORWARD_DEBUG_CLUSTER_LIGHT_COMPLEXITY shows good bounds
around the cone for a variety of orthographic setups).

crates/bevy_pbr/src/light.rs

@@ -1081,20 +1081,12 @@ fn compute_aabb_for_cluster(
 
         // Convert to view space at the cluster near and far planes
         // NOTE: 1.0 is the near plane due to using reverse z projections
-        let p_min = screen_to_view(
-            screen_size,
-            inverse_projection,
-            p_min,
-            1.0 - (ijk.z / cluster_dimensions.z as f32),
-        )
-        .xyz();
-        let p_max = screen_to_view(
-            screen_size,
-            inverse_projection,
-            p_max,
-            1.0 - ((ijk.z + 1.0) / cluster_dimensions.z as f32),
-        )
-        .xyz();
+        let mut p_min = screen_to_view(screen_size, inverse_projection, p_min, 0.0).xyz();
+        let mut p_max = screen_to_view(screen_size, inverse_projection, p_max, 0.0).xyz();
+
+        // calculate cluster depth using z_near and z_far
+        p_min.z = -z_near + (z_near - z_far) * ijk.z / cluster_dimensions.z as f32;
+        p_max.z = -z_near + (z_near - z_far) * (ijk.z + 1.0) / cluster_dimensions.z as f32;
 
         cluster_min = p_min.min(p_max);
         cluster_max = p_min.max(p_max);