Enable pyupgrade, add Grid repr, and other changes #37

Job	Run time
mypy	3m 42s
py3.12 \| macos \| unit tests	10m 21s
py3.12 \| macos \| integration tests	16m 15s
py3.12 \| ubuntu \| unit tests	13m 5s
py3.12 \| ubuntu \| integration tests	17m 59s
py3.12 \| windows \| integration tests	33m 1s
py3.12 \| windows \| unit tests	23m 24s
py3.10 \| ubuntu \| unit tests	11m 51s
py3.11 \| ubuntu \| unit tests	13m 5s
	2h 22m 43s

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