Expose optional texture capabilities in WebGPU #2630

In current WebGPU SPEC the texture format capabilities (e.g. rendering, multisample, resolve, etc) must be supported on all WebGPU implementations and are hard-coded in WebGPU SPEC. Will we have a mechanism to allow optional texture format capabilities?

For example, rgba32float can be used to render HDR, and in WebGL we can know if it is supported with gl.getInternalformatParameter(). But in current WebGPU SPEC we can't support multisampling with rgba32float because of the lack of support on old iOS devices.