Make mapv_into_any() work for ArcArray, resolves #1280 #313

Job	Run time
cargo-careful	1m 55s
cross_test/s390x-unknown-linux-gnu/stable	5m 20s
docs/stable	23s
cross_test/i686-unknown-linux-gnu/stable	1m 27s
clippy/stable	18s
format/nightly	11s
nostd/thumbv6m-none-eabi/stable	17s
tests/stable	2m 54s
tests/beta	3m 3s
tests/nightly	3m 11s
tests/1.64.0	3m 50s
conclusion	1s
	22m 50s

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