Backporting fixes:
- Fix: avoid automatic device detection via serialized tensors when deserializing PyTorchPredictor. 2576 by shubhamkapoor
- Fix Map representation. 2579 by jaheba
- serde: Fix encoding of dtypes. 2586 by jaheba
- Add assertion to split function ensuring valid windows 2587 by MarcelK1102
- Ensure dtype on feat_time in torch DeepAR. 2596 by jaheba
- Expose aggregation method in ensemble NBEATS, fix forecast shape 2598 by lostella
- Fix requirements following breaking change in setuptools 2604 by lostella
- Add gluonts.util.safe_extract 2606 by lostella