Implements specialization keys VIEW_PROJECTION_* in depth prepass for shadow maps

[Lichtso]

Objective

Fixes #20941

Solution

Implemented the missing MeshPipelineKey::VIEW_PROJECTION_* in check_views_lights_need_specialization() and PrepassPipeline::specialize().

Testing

I implemented a Material with a custom shader pipeline which uses these keys and added light sources with shadows_enabled. Before this change the material only appeared in the normal forward pass, after it also appears in the shadows.

[github-actions]

Welcome, new contributor!

Please make sure you've read our contributing guide and we look forward to reviewing your pull request shortly ✨

[atlv24]

this is good, i think i'd extract the match into a variable so that the statement is less crazy looking but good other than that

[atlv24]

alternatively something like this

light_key.set(MeshPipelineKey::VIEW_PROJECTION_ORTHOGRAPHIC | MeshPipelineKey::UNCLIPPED_DEPTH_ORTHO, is_directional_light);
light_key.set(MeshPipelineKey::VIEW_PROJECTION_PERSPECTIVE, !is_directional_light);