Make mapv_into_any() work for ArcArray, resolves #1280 #316

Job	Run time
docs/stable	22s
cross_test/s390x-unknown-linux-gnu/stable	5m 50s
cargo-careful	2m 20s
clippy/stable	23s
cross_test/i686-unknown-linux-gnu/stable	1m 36s
format/nightly	12s
nostd/thumbv6m-none-eabi/stable	16s
tests/stable	3m 0s
tests/beta	2m 49s
tests/nightly	3m 49s
tests/1.64.0	4m 0s
conclusion	1s
	24m 38s

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