to_compact: support uncertainties' Magnitudes #1087

Job	Run time
test-linux (3.9)	1m 28s
test-macos (3.9)	1m 50s
test-linux (3.9, uncertainties==3.1.6)	1m 39s
test-windows (3.9, numpy>=1.21,<2.0.0)	46s
test-macos (3.9, numpy>=1.21,<2.0.0)	2m 47s
test-linux (3.9, uncertainties>=3.1.6,<4.0.0)	1m 39s
test-windows (3.10, numpy>=1.21,<2.0.0)	42s
test-macos (3.10)	2m 5s
test-windows (3.11, numpy>=1.21,<2.0.0)	43s
test-linux (3.9, numpy>=1.21,<2.0.0)	1m 37s
test-macos (3.10, numpy>=1.21,<2.0.0)	2m 50s
test-linux (3.9, numpy>=1.21,<2.0.0, uncertainties==3.1.6)	2m 0s
test-macos (3.11)	2m 14s
test-linux (3.9, numpy>=1.21,<2.0.0, uncertainties>=3.1.6,<4.0.0)	2m 40s
test-macos (3.11, numpy>=1.21,<2.0.0)	2m 11s
test-linux (3.10)	1m 40s
test-linux (3.10, uncertainties==3.1.6)	1m 47s
test-linux (3.10, uncertainties>=3.1.6,<4.0.0)	1m 51s
test-linux (3.10, numpy>=1.21,<2.0.0)	1m 51s
test-linux (3.10, numpy>=1.21,<2.0.0, uncertainties==3.1.6)	2m 7s
test-linux (3.10, numpy>=1.21,<2.0.0, uncertainties>=3.1.6,<4.0.0)	1m 58s
test-linux (3.11)	1m 30s
test-linux (3.11, uncertainties==3.1.6)	1m 31s
test-linux (3.11, uncertainties>=3.1.6,<4.0.0)	1m 31s
test-linux (3.11, numpy>=1.21,<2.0.0)	1m 40s
test-linux (3.11, numpy>=1.21,<2.0.0, uncertainties==3.1.6)	1m 56s
test-linux (3.11, numpy>=1.21,<2.0.0, uncertainties>=3.1.6,<4.0.0)	1m 49s
test-linux (3.9, numpy, matplotlib==2.2.5)	2m 41s
test-linux (3.9, numpy, uncertainties, sparse xarray netCDF4 dask[complete]==2023.4.0 graphviz ba...	2m 41s
	53m 44s

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