Make mapv_into_any() work for ArcArray, resolves #1280 #312

Job	Run time
clippy/stable	17s
format/nightly	11s
cargo-careful	2m 1s
cross_test/s390x-unknown-linux-gnu/stable	5m 40s
cross_test/i686-unknown-linux-gnu/stable	1m 36s
docs/stable	21s
nostd/thumbv6m-none-eabi/stable	18s
tests/stable	2m 42s
tests/beta	2m 52s
tests/nightly	3m 3s
tests/1.64.0	4m 2s
conclusion	1s
	23m 4s

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