Refactor: Move getNoiseShaderSnippet to strands backend

[LalitNarayanYadav]

Addresses #8670

Changes

Refactored getNoiseShaderSnippet to be part of the strands backend instead of individual renderers.

Key updates

• Added getNoiseShaderSnippet to:
  • strands_glslBackend
  • strands_wgslBackend
• Updated strands_api to use:

  strandsContext.backend.getNoiseShaderSnippet()
  

Changes

Removed duplicated implementations from:

• WebGL renderer
• WebGPU renderer
• 2D filter renderer

Reason

Previously, noise() shader support depended on renderer-specific implementations, leading to duplication and tighter coupling.

Moving this logic into the backend:

• centralizes shader utilities
• aligns with backend responsibilities
• improves consistency across renderers

Testing

• Build completes successfully with no errors
• Verified noise() works in shaders without renderer-specific dependencies

PR Checklist

• npm run lint passes
• Inline reference is included / updated
• Unit tests are included / updated