NodeMaterial: Only call setupDepth() with active depth buffer.

[Mugen87]

Related issue: #29797.

Description

This makes sure setupDepth() only configures a depth node if the current framebuffer (custom or default) has a configured depth buffer.

[github-actions]

📦 Bundle size

Full ESM build, minified and gzipped.

	Before	After	Diff
WebGL	692.35 171.47	692.35 171.47	+0 B +0 B
WebGPU	822.12 221.89	822.19 221.91	+69 B +20 B
WebGPU Nodes	821.41 221.74	821.48 221.76	+69 B +22 B

🌳 Bundle size after tree-shaking

Minimal build including a renderer, camera, empty scene, and dependencies.

	Before	After	Diff
WebGL	464.89 112.3	464.89 112.3	+0 B +0 B
WebGPU	542.7 146.82	542.77 146.84	+69 B +24 B
WebGPU Nodes	498.64 136.56	498.71 136.59	+69 B +26 B