Adds conversion between SystemTime and datetime #8139

Job	Run time
fmt	14s
emscripten	0s
check-msrv	7m 14s
semver-checks	2m 36s
python${{ matrix.python-version }}-${{ matrix.platform.python-architecture }} ${{ matrix.platform.os }} rust-${{ matrix.rust }}	0s
clippy/x86_64-apple-darwin/stable	9m 42s
careful	0s
coverage-windows	5s
clippy/x86_64-unknown-linux-gnu/stable	8m 9s
coverage-macos	8s
clippy/powerpc64le-unknown-linux-gnu/stable	7m 33s
coverage-ubuntu	11m 35s
clippy/s390x-unknown-linux-gnu/stable	8m 3s
clippy/wasm32-wasi/stable	7m 18s
clippy/x86_64-pc-windows-msvc/stable	10m 47s
test-debug	9m 11s
clippy/i686-pc-windows-msvc/stable	10m 40s
valgrind	0s
clippy/x86_64-unknown-linux-gnu/beta	8m 43s
docsrs	0s
python3.12-x64 ubuntu-latest rust-stable / build	6m 50s
python3.12-x64 windows-latest rust-stable / build	11m 25s
python3.12-x86 windows-latest rust-stable / build	10m 10s
python3.12-x64 macos-latest rust-stable / build	8m 33s
python3.12-x64 ubuntu-latest rust-nightly / build	7m 36s
conclusion	1s
	2h 26m 33s

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