Implement Sync for ArrayParts #559

Job	Run time
clippy/stable	23s
Pass MSRV values to other jobs	4s
cargo-careful	2m 5s
format/nightly	14s
docs/nightly	21s
nostd/thumbv6m-none-eabi/stable	17s
miri	11m 10s
cross_test/i686-unknown-linux-gnu/stable	2m 13s
cross_test/s390x-unknown-linux-gnu/stable	9m 56s
tests/stable	2m 30s
tests/beta	2m 38s
tests/1.64.0	6m 39s
blas-msrv	58s
tests/nightly	3m 11s
conclusion	0s
	42m 39s

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