Chronos will support the new pytorch model `NBeatsx`

[liangs6212]

Description: Currently, we have supported the nbeats model, some details are given below:

• nbeats is extremely fast for training and inference.
• Friendly to time series datasets with seasonal and trend patterns.
• A univariate multistep model. The univariate multi-step model cannot solve the actual demand, so Nbeatsx was introduced.