Add uniform decorator for improving custom material code

[HypnosNova]

With uniform decorator, it will be easier for create uniform property in material class.

Features:

1. support define glsl variable name

class XXXMaterial extends BaseMaterial {
  // In this case, decorator only know baseColor is a Color type. So in glsl code, the variable name is the same as property name 'baseColor'
  @uniform(ShaderUniformType.Color)
  baseColor: Color = new Color(1, 1, 1, 1);
}

class XXXMaterial2 extends BaseMaterial {
  // In this case, decorator has second param, and varName in glsl is 'material_BaseColor' instead of using the same property name in js
  @uniform(ShaderUniformType.Color, {
    varName: 'material_BaseColor'
  })
  baseColor: Color = new Color(1, 1, 1, 1);
}

2. support macro

class XXXMaterial extends BaseMaterial {
  // In this case, decorator knows if we set the texture, we should also need to enable MATERIAL_HAS_BASETEXTURE macro. If we remove the texture, we should disable the macro.
  @uniform(ShaderUniformType.Texture, {
    varName: "material_BaseColor",
    macroName: "MATERIAL_HAS_BASETEXTURE"
  })
  baseTexture: Texture2D;
}

// the above code logic is the same as following code:
class UnlitMaterial extends BaseMaterial {
  /**
   * Base texture.
   */
  get baseTexture(): Texture2D {
    return <Texture2D>this.shaderData.getTexture(UnlitMaterial._baseTextureProp);
  }

  set baseTexture(value: Texture2D) {
    this.shaderData.setTexture(UnlitMaterial._baseTextureProp, value);
    if (value) {
      this.shaderData.enableMacro(UnlitMaterial._baseTextureMacro);
    } else {
      this.shaderData.disableMacro(UnlitMaterial._baseTextureMacro);
    }
  }
}

3. support keeping reference

class XXXMaterial extends BaseMaterial {
  @uniform(ShaderUniformType.Color, {
    keepRef: true
  })
  baseColor: Color = new Color(1, 1, 1, 1);
}

// If we keepRef, the baseColor will not be changed reference but only copy data just like:
const material = new XXXMaterial();
const newColor = new Color(0,0,0,0);
material.baseColor = newColor; // This code will not change reference
material.baseColor === newColor // false, but the baseColor's data is 0,0,0,0

[codecov]

Codecov Report

Patch coverage: 73.99% and project coverage change: +0.59% 🎉

Comparison is base (ef443a3) 61.37% compared to head (47a8875) 61.97%.
Report is 28 commits behind head on dev/1.1.

❗ Current head 47a8875 differs from pull request most recent head dc6b8e8. Consider uploading reports for the commit dc6b8e8 to get more accurate results

Additional details and impacted files

@@             Coverage Diff             @@
##           dev/1.1    #1713      +/-   ##
===========================================
+ Coverage    61.37%   61.97%   +0.59%     
===========================================
  Files          410      432      +22     
  Lines        21834    22447     +613     
  Branches      3140     3190      +50     
===========================================
+ Hits         13401    13911     +510     
- Misses        7244     7315      +71     
- Partials      1189     1221      +32     

Files Changed	Coverage Δ
packages/core/src/asset/Loader.ts	83.33% <ø> (ø)
packages/core/src/material/BlinnPhongMaterial.ts	94.11% <ø> (+3.20%)	⬆️
packages/core/src/material/Material.ts	94.59% <0.00%> (-2.63%)	⬇️
packages/core/src/material/PBRBaseMaterial.ts	81.25% <ø> (+0.98%)	⬆️
packages/core/src/material/PBRMaterial.ts	72.72% <ø> (-12.28%)	⬇️
packages/core/src/material/PBRSpecularMaterial.ts	87.50% <ø> (-1.98%)	⬇️
packages/core/src/material/UnlitMaterial.ts	90.90% <ø> (+3.40%)	⬆️
...ckages/core/src/shadow/CascadedShadowCasterPass.ts	31.97% <ø> (ø)
.../loader/src/gltf/extensions/GLTFExtensionParser.ts	55.55% <ø> (-4.45%)	⬇️
...ader/src/gltf/extensions/KHR_materials_variants.ts	20.00% <0.00%> (ø)
... and 33 more

... and 33 files with indirect coverage changes

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.