Remove `python-gil` requirement and enable free-threaded Python #6047

Job	Run time
build_linux (3.13)	6m 42s
build_linux (3.12)	6m 38s
build_linux (3.14)	7m 14s
build_linux (3.11)	5m 32s
build_windows (3.14, 3.14.* *_cp314)	11m 25s
build_windows (3.12)	10m 47s
build_windows (3.13)	9m 53s
build_windows (3.11)	11m 12s
build_linux (3.10)	6m 50s
build_windows (3.10)	10m 55s
build_linux (3.14, 3.14.* *_cp314)	7m 5s
build_windows (3.14)	12m 4s
test_examples_linux (3.11, false, ubuntu-22.04)	9m 26s
upload_linux	0s
Clean up anaconda packages	-1s
upload_windows	-1s
build_linux (3.10)	6m 40s
build_linux (3.11)	6m 33s
build_windows (3.11)	10m 57s
build_linux (3.14, 3.14.* *_cp314)	7m 3s
build_linux (3.14)	5m 25s
build_windows (3.13)	10m 35s
build_windows (3.12)	11m 20s
build_linux (3.12)	6m 45s
build_linux (3.13)	6m 54s
build_windows (3.10)	11m 36s
build_windows (3.14)	11m 36s
build_windows (3.14, 3.14.* *_cp314)	10m 57s
test_examples_linux (3.11, false, ubuntu-22.04)	9m 25s
upload_linux	0s
upload_windows	0s
Clean up anaconda packages	-1s
	3h 51m 26s

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