Refactor check_light_mesh_visibility for performance #2

[re0312]

Objective

• Second part of Refactor check_light_mesh_visibility for performance  #13900
• based on Refactor check_light_mesh_visibility for performance #1 #13905

Solution

• check_dir_light_mesh_visibility defers setting the entity's ViewVisibility so that Bevy can schedule it to run in parallel with check_point_light_mesh_visibility.

• Reduce HashMap lookups for directional light checking as much as possible

• Use par_iter to parallelize the checking process within each system.

[re0312]

Marking as draft until #13905 get merged.

[kristoff3r]

Looks ok to me now, and I tested that many_cubes with shadows still works

[IceSentry]

I'm not super familiar with this code, but the implementation makes sense to me and the perf gain look pretty good.

I tested various examples and they all seemed to work correctly.