split `PyCell` and `PyClassObject` concepts #8860

Job	Run time
fmt	11s
check-msrv	10m 10s
semver-checks	33s
clippy/x86_64-apple-darwin/stable	20m 19s
careful	0s
python${{ matrix.python-version }}-${{ matrix.platform.python-architecture }} ${{ matrix.platform.os }} rust-${{ matrix.rust }}	0s
clippy/x86_64-unknown-linux-gnu/stable	12m 39s
coverage-windows	7s
clippy/powerpc64le-unknown-linux-gnu/stable	11m 19s
coverage-macos	6s
clippy/s390x-unknown-linux-gnu/stable	11m 33s
docsrs	0s
coverage-ubuntu	12m 5s
test-debug	9m 9s
clippy/wasm32-wasi/stable	11m 19s
clippy/x86_64-pc-windows-msvc/stable	16m 0s
clippy/i686-pc-windows-msvc/stable	15m 28s
valgrind	0s
clippy/x86_64-unknown-linux-gnu/beta	13m 46s
check-feature-powerset	0s
emscripten	0s
test-cross-compilation ${{ matrix.os }} -> ${{ matrix.target }}	0s
test-cross-compilation-windows	0s
test-version-limits	0s
python3.12-x64 ubuntu-latest rust-stable / build	7m 32s
python3.12-x64 windows-latest rust-stable / build	11m 44s
python3.12-x86 windows-latest rust-stable / build	10m 14s
python3.12-x64 macos-latest rust-stable / build	8m 53s
python3.12-x64 ubuntu-latest rust-nightly / build	8m 9s
conclusion	1s
	3h 11m 17s

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