Add py free-threaded support #1693

Job	Run time
Build and test with .NET	21s
Build and test cmake:gcc-old	39s
Build and test cmake:clang:asan	58s
Build and test cmake:clang	45s
Build and test cmake:static	1m 5s
Build and test cmake:clang:tsan	1m 6s
Build and test cmake-osx:clang	25s
Build and test cmake:clang-old	49s
Build and test cmake:gcc	42s
Build and test cmake:qemu-arm-neon-gcc	2m 48s
Build and test cmake-win64:msvc-dbg	1m 18s
Build and test cmake:package	1m 8s
Build and test cmake-ios:clang	20s
Build and test python3.14t:clang	38s
Build and test python3.14:clang	31s
Build and test bazel:go	1m 24s
Build and test cmake-osx:gcc	23s
Build and test bazel:research	42s
Build and test bazel-osx:java	3m 19s
Build and test python3.14-win	23s
Build and test bazel:root	1m 1s
Build and test maven	1m 3s
Build and test bazel-osx:go	1m 17s
Build and test fuzz:clang	54s
Build and test cmake:clang:ubsan	59s
Build and test bazel-win:root	1m 20s
Build and test bazel-osx:root	57s
Build and test bazel-osx:research	1m 3s
Build and test cmake-win64:msvc-rel	49s
Build and test bazel:java	2m 20s
Build and test bazel-win:research	2m 49s
	34m 16s

Provide feedback