Gluonts

Backporting fixes:
- [torch] Return a model even if callback has no best model path 2952 by kashif
- Move from pytorch_lightning to lightning 3013 by shchur

Backporting fixes:
- Raise warning in QuantileForecast.mean when mean is not there 2843 by lostella
- [R] Bug fix for running R methods via ParallelizedPredictor 2983 by rshyamsundar
- Fix Forecast plot method 3006 by lostella

Backporting fixes:
- Turn type comparison into isinstance 2958 by lostella
- Fix Cython version in XGBoost tests 2966 by lostella
- Clean up RepresentablePredictor 2967 by lostella
- Fix: use isinstance instead of type comparison 2973 by melopeo
- Fix ArrowDecoder.decode to return instead of yield 2976 by lostella
- Unpin pyarrow version 2977 by lostella

Backporting fixes:
- Zebras: Fix index handling of SplitFrame.resize. 2938 by jaheba
- Docs: fix missing values use-case in tutorial for PandasDataset 2941 by cneely33
- Ignore F403 errors in preludes. 2948 by jaheba
- Fix: prevent accumulation of SelectFields in PyTorchPredictor 2951 by Cameronwood611
- [Docs] fix link to NPTS implementation 2953 by lostella

Backporting fixes:
- Fix NaNs in seasonal error 2894 by gorold
- Filter unused fields during inference 2905 by abdulfatir
- Define __repr__ instead of __str__ for PandasDataset 2906 by lostella
- Fix typo in background.md 2907 by tnixon
- Fix another typo in background.md 2908 by tnixon

Backporting fixes:
- Speedup is_uniform for PandasDataset. 2878 by jaheba
- Fix docstrings in torch lightning modules 2880 by lostella
- Fix default scale in torch DeepAR 2885 by lostella