CI: test all crates with `--no-default-features` #843

Job	Run time
build (1.56.0, armv7a-none-eabi)	4m 37s
test (i686-unknown-linux-gnu, 1.56.0, sudo apt update && sudo apt install gcc-multilib)	6m 21s
build (1.56.0, thumbv7em-none-eabi)	4m 46s
test (i686-unknown-linux-gnu, stable, sudo apt update && sudo apt install gcc-multilib)	1m 1s
build (1.56.0, wasm32-unknown-unknown)	5m 49s
test (x86_64-unknown-linux-gnu, 1.56.0)	6m 5s
build (stable, armv7a-none-eabi)	14s
test (x86_64-unknown-linux-gnu, stable)	33s
build (stable, thumbv7em-none-eabi)	18s
build (stable, wasm32-unknown-unknown)	12s
	29m 56s

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