WebGLRenderer: Clean up setupRenderBufferStorage

[mrdoob]

Description

• Renamed isMultisample parameter to useMultisample for clarity
• Sample count is now derived from renderTarget inside the function
• Unified condition ordering in both depth and color buffer branches

[github-actions]

📦 Bundle size

Full ESM build, minified and gzipped.

	Before	After	Diff
WebGL	350.3 83.02	350.28 83	-13 B -12 B
WebGPU	616.03 171	616.03 171	+0 B +0 B
WebGPU Nodes	614.64 170.74	614.64 170.74	+0 B +0 B

🌳 Bundle size after tree-shaking

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

	Before	After	Diff
WebGL	482.34 117.82	482.33 117.81	-12 B -10 B
WebGPU	687.42 186.76	687.42 186.76	+0 B +0 B
WebGPU Nodes	637.26 173.94	637.26 173.94	+0 B +0 B