Add `.shrink_to_fit()` for `Array` #262

Job	Run time
docs/stable	19s
clippy/stable	13s
cross_test/s390x-unknown-linux-gnu/stable	5m 43s
cargo-careful	1m 59s
cross_test/i686-unknown-linux-gnu/stable	1m 33s
format/nightly	15s
nostd/thumbv6m-none-eabi/stable	8s
tests/stable	2m 33s
tests/beta	3m 0s
tests/nightly	3m 19s
tests/1.64.0	4m 8s
conclusion	2s
	23m 12s

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