Refactor/metrics (#2284) #933

Job	Run time
lint	57s
docs	3m 59s
tests (macos-latest, 3.8, core)	30m 9s
tests (macos-latest, 3.8, torch)	46m 56s
check-examples (00-quickstart.ipynb)	3m 52s
tests (macos-latest, 3.8, all)	33m 18s
check-examples (01-multi-time-series-and-covariates.ipynb)	3m 52s
tests (macos-latest, 3.10, core)	15m 56s
check-examples (02-data-processing.ipynb)	3m 52s
tests (macos-latest, 3.10, torch)	41m 46s
check-examples (03-FFT-examples.ipynb)	3m 51s
tests (macos-latest, 3.10, all)	37m 20s
check-examples (04-RNN-examples.ipynb)	3m 52s
tests (ubuntu-latest, 3.8, core)	14m 33s
check-examples (05-TCN-examples.ipynb)	3m 53s
tests (ubuntu-latest, 3.8, torch)	32m 40s
check-examples (06-Transformer-examples.ipynb)	3m 52s
tests (ubuntu-latest, 3.8, all)	29m 40s
check-examples (07-NBEATS-examples.ipynb)	3m 52s
tests (ubuntu-latest, 3.10, core)	15m 8s
check-examples (08-DeepAR-examples.ipynb)	3m 53s
tests (ubuntu-latest, 3.10, torch)	29m 27s
check-examples (09-DeepTCN-examples.ipynb)	3m 52s
tests (ubuntu-latest, 3.10, all)	35m 8s
check-examples (10-Kalman-filter-examples.ipynb)	3m 52s
check-examples (11-GP-filter-examples.ipynb)	3m 52s
check-examples (12-Dynamic-Time-Warping-example.ipynb)	3m 52s
check-examples (13-TFT-examples.ipynb)	3m 53s
check-examples (15-static-covariates.ipynb)	3m 49s
check-examples (16-hierarchical-reconciliation.ipynb)	3m 34s
check-examples (18-TiDE-examples.ipynb)	3m 50s
check-examples (19-EnsembleModel-examples.ipynb)	3m 51s
check-examples (20-RegressionModel-examples.ipynb)	3m 51s
	7h 20m 2s

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