Let the user instantiate custom assets inside a container

[hai-vr]

Let the user instantiate custom assets inside a container.

This can let the user generate assets of their own that will be cleaned on every generation.

Example:

MeshRenderer mr;

Material modifiedAsset = aac.CopyAsset(mr.materials[0]);
modifiedAsset.SetColor("_Color", Color.green);

aac.NewClip().SwappingMaterial(mr, 0, modifiedAsset);