Make the ffi crate `no_std` #17019

Job	Run time
fmt	23s
resolve	6s
semver-checks	25s
pytests-type-checking (mypy)	45s
check-msrv	4m 15s
pytests-type-checking (pyrefly)	43s
test-introspection-pr	52s
clippy/i686-pc-windows-msvc/stable	4m 12s
clippy/x86_64-unknown-linux-gnu/stable	4m 26s
clippy/aarch64-unknown-linux-gnu/stable	4m 16s
clippy/x86_64-pc-windows-msvc/stable	4m 3s
clippy/aarch64-apple-darwin/stable	4m 1s
clippy/wasm32-wasip1/stable	4m 16s
clippy/powerpc64le-unknown-linux-gnu/stable	4m 8s
clippy/s390x-unknown-linux-gnu/stable	4m 16s
clippy/x86_64-unknown-linux-gnu/beta	4m 16s
clippy/aarch64-pc-windows-msvc/stable	4m 7s
emscripten	-1s
python3.14-x64 windows-latest rust-stable / build	1m 22s
python3.14-arm64 windows-11-arm rust-stable / build	2m 15s
python3.14-x86 windows-latest rust-stable / build	1m 18s
python3.14t-x64 ubuntu-latest rust-stable / build	1m 49s
python3.14-x64 ubuntu-latest rust-nightly / build	1m 37s
python3.14-arm64 macos-latest rust-stable / build	1m 2s
python3.14-arm64 ubuntu-24.04-arm rust-stable / build	2m 8s
python3.14-x64 ubuntu-latest rust-stable / build	2m 11s
test-version-limits	-1s
test-cross-compilation ${{ matrix.os }} -> ${{ matrix.target }}	-1s
python${{ matrix.python-version }}-${{ matrix.platform.python-architecture }} ${{ matrix.platform.os }} rust-${{ matrix.rust }}	-1s
test-introspection	0s
valgrind	-1s
check-feature-powerset ${{ matrix.rust }}	0s
careful	0s
test-debug	-1s
docsrs	-1s
test-cross-compilation-windows	0s
wasm32-wasip1	0s
conclusion	3s
	1h 3m 8s

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