Add tests for `From` impls on `Box` and `Vec` #418

Job	Run time
coverage	25s
clippy	20s
miri (x86_64-unknown-linux-gnu)	48s
doc	20s
miri (s390x-unknown-linux-gnu)	1m 6s
test (1.85.0)	53s
test (stable)	46s
build (1.85.0, armv7a-none-eabi)	1m 16s
build (stable, wasm32-unknown-unknown)	1m 10s
rustfmt	4s
careful	58s
build (stable, armv7a-none-eabi)	1m 11s
build (1.85.0, thumbv7em-none-eabi)	1m 22s
build (stable, thumbv7em-none-eabi)	1m 10s
build (1.85.0, wasm32-unknown-unknown)	1m 19s
	13m 8s

Provide feedback