Remove `python-gil` requirement and enable free-threaded Python #6040

Job	Run time
build_linux (3.14, false)	5m 57s
build_linux (3.13, false)	5m 1s
build_linux (3.14, true)	5m 52s
build_linux (3.10, false)	4m 52s
build_windows (3.13, false)	11m 7s
build_windows (3.14, false)	11m 5s
build_linux (3.11, false)	5m 9s
build_windows (3.10, false)	9m 48s
build_windows (3.12, false)	11m 11s
build_windows (3.14, true)	10m 37s
build_linux (3.12, false)	6m 20s
build_windows (3.11, false)	11m 8s
test_examples_linux (3.11, false, ubuntu-22.04)	8m 48s
test_linux (3.11, false, false, ubuntu-22.04)	56s
test_linux (3.13, false, false, ubuntu-22.04)	56s
test_linux (3.14, false, false, ubuntu-22.04)	56s
test_linux (3.10, false, false, ubuntu-22.04)	1m 8s
test_linux (3.12, false, false, ubuntu-22.04)	1m 2s
test_linux (3.14, true, false, ubuntu-22.04)	57s
upload_linux	0s
test_windows (3.12, false, false, windows-latest)	5m 36s
test_windows (3.13, false, false, windows-latest)	4m 16s
test_windows (3.11, false, false, windows-latest)	5m 16s
test_windows (3.14, true, false, windows-latest)	4m 0s
test_windows (3.14, false, false, windows-latest)	3m 56s
test_windows (3.10, false, false, windows-latest)	4m 20s
upload_windows	-1s
Clean up anaconda packages	0s
	2h 20m 13s

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