Remove `python-gil` requirement and enable free-threaded Python #6311

Job	Run time
build_linux (3.12)	5m 50s
build_windows (3.12)	8m 42s
build_linux (3.11)	6m 2s
build_linux (3.13)	5m 49s
build_windows (3.10)	9m 21s
build_linux (3.10)	6m 49s
build_linux (3.14)	5m 49s
build_windows (3.14, 3.14.* *_cp314)	8m 30s
build_windows (3.11)	8m 36s
build_windows (3.14)	8m 9s
build_windows (3.13)	8m 25s
build_linux (3.14, 3.14.* *_cp314)	5m 58s
test_examples_linux (3.14, false, ubuntu-latest)	5m 28s
test_linux (3.12, false, ubuntu-latest)	3m 6s
test_linux (3.14, 3.14.* *_cp314, false, ubuntu-22.04)	2m 53s
test_linux (3.10, false, ubuntu-latest)	3m 18s
test_linux (3.11, false, ubuntu-latest)	2m 33s
test_linux (3.14, false, ubuntu-latest)	3m 12s
test_linux (3.13, false, ubuntu-latest)	2m 52s
test_windows (3.10, false, windows-latest)	3m 2s
test_windows (3.14, false, windows-latest)	3m 33s
test_windows (3.13, false, windows-latest)	3m 25s
test_windows (3.14, 3.14.* *_cp314, false, windows-latest)	3m 49s
test_windows (3.12, false, windows-latest)	3m 10s
test_windows (3.11, false, windows-latest)	4m 4s
upload_linux	-1s
upload_windows	0s
Clean up anaconda packages	0s
	2h 12m 24s

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