Material: Deprecate material.morphTargets=true and material.morphNormals=true?

[donmccurdy]

Similar to #22146 and #21788, both properties could be inferred from the parent Mesh, without requiring separate boolean flags on the material. Along with the recent removal of .skinning, this should help avoid situations where the user replaces a material provided by a loader and doesn't understand why the model stops animating.

Earlier threads proposed removing other properties that could be inferred (e.g. flatShading, vertexColors), but there has been some push-back against removing those and I don't feel strongly either way.

[WestLangley]

Hmm... so a material can no longer be compiled without a geometry. We started down that path with vertexAlphas... 🤔

[Mugen87]

Actually vertexAlphas was not the first step in that direction. You need information from many entities (renderer, scene, 3D object, material and geometry) in order to compile a shader program. In WebGPURenderer we maintain a node builder per render item right from the beginning in order to determine the correct shader program.

Removing morphTargets and morphNormals is only a logical consequence after #21788.