Add `.shrink_to_fit()` for `Array` #261

Job	Run time
docs/stable	12s
cross_test/s390x-unknown-linux-gnu/stable	6m 4s
cargo-careful	2m 11s
cross_test/i686-unknown-linux-gnu/stable	2m 4s
clippy/stable	13s
format/nightly	11s
nostd/thumbv6m-none-eabi/stable	10s
tests/stable	25s
tests/beta	35s
tests/nightly	35s
tests/1.64.0	31s
conclusion	1s
	13m 12s

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