Material asset miss texture asset after v1.40.5+ engine

Description

This happen with the following conditions:

1. material asset refer texture asset and cubemap asset.
2. texture asset with negative asset id
3. cubemap asset loaded after the refered texture asset.

When you load the material asset, the material will miss texture.
Here is a screenshot:

Here is the test project and the code snippet:

https://playcanvas.com/project/700222/overview

var textureAsset = new pc.Asset('t', 'texture', { url: 'https://raw.githubusercontent.com/nidorx/matcaps/master/64/28292A_D3DAE5_A3ACB8_818183-64px.png' });
var cubemapAsset = pc.app.assets.list().find(a => a.type === 'cubemap' && !a.loaded);
var materialAsset = new pc.Asset('m', 'material', null, { diffuseMap: textureAsset.id, cubeMap: cubemapAsset.id });
var onLoaded = () => {
    if (textureAsset.loaded && cubemapAsset.loaded && materialAsset.loaded) {
        console.log('texture: ', textureAsset.resource);
        console.log('material.difuseMap', materialAsset.resource.diffuseMap);
        console.log('material.cubeMap', materialAsset.resource.cubeMap);
    }
}

textureAsset.ready(onLoaded);
cubemapAsset.ready(onLoaded);
materialAsset.ready(onLoaded);
pc.app.assets.add(textureAsset);
pc.app.assets.add(materialAsset);
pc.app.assets.load(materialAsset);

Reason

In #3074 , @raytranuk remove the following code:

    _assignTexture(parameterName, materialAsset, texture) {
-        materialAsset.data[parameterName] = texture;
        materialAsset.resource[parameterName] = texture;
    }

In JsonStandardMaterialParser:

 // initialize material values from the input data
 for (const key in data) {
    const type = standardMaterialParameterTypes[key];
    const value = data[key];

    // .......
+    if (type === 'texture') {
+        if (value instanceof Texture) {
+            material[key] = value;
+        } else if (!(material[key] instanceof Texture && typeof(value) === 'number' && value > 0)) {
+            material[key] = null;
+        }
+    }

    // ......
}

The engine will check materialAsset.data's texture type and it may override the texture field to null if the texture asset id is negative.

In MaterialHandler,

_onCubemapLoad(parameterName, materialAsset, cubemapAsset) {
    this._assignCubemap(parameterName, materialAsset, cubemapAsset.resources);
    this._parser.initialize(materialAsset.resource, materialAsset.data);
}

when the cubemap asset loaded, it will call JsonStandardMaterialParser#initialize again, and if the cubemap asset is loaded after the texture asset, it will set the texture field to null.

Maybe this will affect engine user only (like me 😭 ).

Start with src/resources/material.js and src/resources/parser/material/json-standard-material.js, then reproduce the failure using the linked project or the JavaScript snippet. Trace material initialization when the cubemap loads after the texture, and consider the issue complete when the material retains its texture and cubemap resources in that order.