Add `From<Array>` conversions for `Box`/`Vec` #286

Job	Run time
careful	59s
build (1.85.0, thumbv7em-none-eabi)	21s
build (stable, thumbv7em-none-eabi)	19s
build (1.85.0, armv7a-none-eabi)	20s
build (1.85.0, wasm32-unknown-unknown)	19s
build (stable, armv7a-none-eabi)	19s
test (stable)	20s
clippy	15s
doc	11s
miri (x86_64-unknown-linux-gnu)	38s
test (1.85.0)	24s
miri (s390x-unknown-linux-gnu)	54s
build (stable, wasm32-unknown-unknown)	30s
rustfmt	6s
	5m 55s

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