[Feat] Improving the getColor method in IconLayer

Target Use Case

Current getColor implementation with mask:true has critical limitations:

1. Only works with binary masks - completely replaces all non-transparent pixels with solid color
2. Destroys image details - cannot preserve:
   • Multi-tone icons (e.g. logos with shadows)
   • Built-in color schemes
3. Performance overhead - requires generating separate atlases for each color variation

Proposal

Introduce alternative color blending via tint mode when mask:false:

new IconLayer({
  getColor: d => [r, g, b, a], // Applies as tint color
  iconMapping: {
    customIcon: {
      mask: false, // Enables tint blending
      // Original colors are preserved but blended with tint
    }
  }
});

tint Mode vs Current mask:true

Start with the IconLayer getColor implementation and iconMapping mask behavior described in the issue. Define how mask:false tint blending should preserve multicolor and gradient icon details, support dynamic updates, and avoid separate atlas generation; the payload does not name files or tests.