CI: test all crates with `--no-default-features` #846

Job	Run time
test (i686-unknown-linux-gnu, 1.56.0, sudo apt update && sudo apt install gcc-multilib)	6m 23s
build (1.56.0, armv7a-none-eabi)	6m 7s
test (i686-unknown-linux-gnu, stable, sudo apt update && sudo apt install gcc-multilib)	58s
build (1.56.0, thumbv7em-none-eabi)	4m 44s
test (x86_64-unknown-linux-gnu, 1.56.0)	4m 52s
build (1.56.0, wasm32-unknown-unknown)	4m 42s
test (x86_64-unknown-linux-gnu, stable)	22s
build (stable, armv7a-none-eabi)	16s
build (stable, thumbv7em-none-eabi)	2m 6s
build (stable, wasm32-unknown-unknown)	11s
	30m 41s

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