Update Cython to v3.1 (#887) #1209

Job	Run time
Run tests with coverage	2m 54s
Run tests (3.10)	1m 50s
Run tests (3.9)	1m 52s
Run tests with different pydantic versions	3m 5s
Run tests (3.11)	1m 49s
Run tests (3.8)	1m 50s
Run linters (pydocstyle)	1m 29s
Run linters (mypy)	1m 34s
Run tests (3.12)	1m 52s
Run tests (3.13)	1m 51s
Run linters (flake8)	1m 32s
Run linters (pylint)	1m 35s
	23m 13s

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