[MoltenVK] The depth buffer is broken on iOS

[Markos-Th09]

The depth buffer is completely broken when running on iOS, and background elements (such as skyboxes, distant structures, and inner terrain walls) are actively rendered on top of closer foreground geometry.

[Markos-Th09]

Testing the native Metal backend by squidbus (hedge-dev#1648), the depth sorting issue does not seem to present itself.

This indicates that the bug is likely not as complicated as initially thought. Since the native Metal pipeline maps the depth coordinates and attachments perfectly, the problem is likely highly localized to discrepancies unique to the Vulkan-to-MoltenVK translation layer on iOS drivers.