Add py free-threaded support #1700

Job	Run time
Build and test with .NET	15s
Build and test cmake:clang	47s
Build and test cmake:gcc	43s
Build and test cmake:clang-old	54s
Build and test cmake:clang:asan	59s
Build and test cmake:clang:tsan	53s
Build and test cmake:gcc-old	38s
Build and test cmake:package	1m 1s
Build and test cmake:clang:ubsan	1m 6s
Build and test cmake:static	43s
Build and test cmake-osx:gcc	34s
Build and test cmake-win64:msvc-rel	52s
Build and test cmake-osx:clang	28s
Build and test cmake:qemu-arm-neon-gcc	1m 40s
Build and test cmake-win64:msvc-dbg	50s
Build and test fuzz:clang	1m 5s
Build and test python3.14t:clang	39s
Build and test maven	58s
Build and test cmake-ios:clang	26s
Build and test bazel:root	1m 38s
Build and test bazel:go	1m 19s
Build and test python3.14:clang	27s
Build and test python3.14-win	23s
Build and test bazel-osx:research	1m 20s
Build and test bazel:java	2m 41s
Build and test bazel:research	42s
Build and test bazel-osx:java	2m 50s
Build and test bazel-osx:go	1m 41s
Build and test bazel-osx:root	1m 4s
Build and test bazel-win:research	1m 7s
Build and test bazel-win:root	1m 59s
	32m 42s

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