Add FFI definitions from `pythread.h` #12400

Job	Run time
fmt	13s
resolve	4s
check-msrv	33s
semver-checks	24s
clippy/aarch64-apple-darwin/stable	37s
python${{ matrix.python-version }}-${{ matrix.platform.python-architecture }} ${{ matrix.platform.os }} rust-${{ matrix.rust }}	0s
clippy/x86_64-unknown-linux-gnu/stable	35s
valgrind	0s
clippy/powerpc64le-unknown-linux-gnu/stable	36s
clippy/s390x-unknown-linux-gnu/stable	35s
coverage windows-latest	22s
clippy/wasm32-wasip1/stable	36s
docsrs	0s
clippy/x86_64-pc-windows-msvc/stable	28s
coverage macos-latest	25s
coverage ubuntu-latest	37s
clippy/i686-pc-windows-msvc/stable	28s
emscripten	0s
clippy/x86_64-unknown-linux-gnu/beta	37s
careful	0s
Free threaded tests - ubuntu-latest	23s
Free threaded tests - macos-latest	23s
check-feature-powerset ${{ matrix.rust }}	0s
Free threaded tests - windows-latest	20s
test-cross-compilation ${{ matrix.os }} -> ${{ matrix.target }}	0s
test-debug	0s
test-version-limits	0s
test-cross-compilation-windows	0s
python3.12-x64 ubuntu-latest rust-nightly / build	35s
python3.12-x64 macos-13 rust-stable / build	22s
python3.12-x64 ubuntu-latest rust-stable / build	1s
python3.12-x86 windows-latest rust-stable / build	1s
python3.12-x64 windows-latest rust-stable / build	1s
python3.12-arm64 macos-latest rust-stable / build	1s
conclusion	1s
	9m 18s

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