Add FFI definitions from `pythread.h` #12401

Job	Run time
resolve	4s
fmt	17s
check-msrv	1m 14s
semver-checks	2m 40s
python${{ matrix.python-version }}-${{ matrix.platform.python-architecture }} ${{ matrix.platform.os }} rust-${{ matrix.rust }}	0s
clippy/aarch64-apple-darwin/stable	1m 20s
careful	0s
clippy/x86_64-unknown-linux-gnu/stable	1m 20s
coverage windows-latest	17m 20s
Free threaded tests - ubuntu-latest	10m 12s
clippy/powerpc64le-unknown-linux-gnu/stable	1m 20s
coverage macos-latest	8m 43s
Free threaded tests - macos-latest	7m 21s
clippy/s390x-unknown-linux-gnu/stable	1m 19s
coverage ubuntu-latest	12m 15s
Free threaded tests - windows-latest	15m 51s
clippy/wasm32-wasip1/stable	1m 3s
valgrind	0s
clippy/x86_64-pc-windows-msvc/stable	1m 4s
clippy/i686-pc-windows-msvc/stable	1m 3s
clippy/x86_64-unknown-linux-gnu/beta	1m 19s
docsrs	0s
emscripten	0s
test-debug	0s
check-feature-powerset ${{ matrix.rust }}	0s
test-version-limits	0s
test-cross-compilation ${{ matrix.os }} -> ${{ matrix.target }}	0s
test-cross-compilation-windows	0s
python3.12-x64 ubuntu-latest rust-nightly / build	7m 50s
python3.12-arm64 macos-latest rust-stable / build	8m 0s
python3.12-x64 macos-13 rust-stable / build	16m 6s
python3.12-x64 ubuntu-latest rust-stable / build	9m 49s
python3.12-x86 windows-latest rust-stable / build	12m 36s
python3.12-x64 windows-latest rust-stable / build	16m 43s
conclusion	1s
	2h 36m 50s

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