Remove `python-gil` requirement and enable free-threaded Python #6045

Job	Run time
build_linux (3.11)	5m 35s
build_windows (3.12)	12m 46s
build_linux (3.14)	5m 27s
build_linux (3.10)	5m 27s
build_linux (3.13)	5m 26s
build_windows (3.14)	9m 29s
build_linux (3.12)	5m 36s
build_windows (3.13)	10m 22s
build_windows (3.11)	11m 17s
build_windows (3.10)	12m 6s
test_examples_linux (3.11, false, ubuntu-22.04)	8m 51s
test_linux (3.13, false, ubuntu-22.04)	2m 48s
test_linux (3.14, false, ubuntu-22.04)	2m 39s
test_linux (3.10, false, ubuntu-22.04)	2m 43s
test_linux (3.12, false, ubuntu-22.04)	3m 14s
test_linux (3.11, false, ubuntu-22.04)	2m 58s
upload_linux	0s
test_windows (3.10, false, windows-latest)	4m 10s
test_windows (3.13, false, windows-latest)	4m 37s
test_windows (3.12, false, windows-latest)	4m 16s
test_windows (3.14, false, windows-latest)	4m 13s
test_windows (3.11, false, windows-latest)	4m 8s
Clean up anaconda packages	0s
upload_windows	0s
	2h 8m 8s

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