Adds Miri to CI/CD #320

Job	Run time
clippy/stable	23s
nostd/thumbv6m-none-eabi/stable	16s
format/nightly	15s
tests/stable	2m 45s
tests/beta	2m 51s
cargo-careful	1m 55s
cross_test/s390x-unknown-linux-gnu/stable	5m 32s
docs/stable	23s
tests/nightly	3m 3s
cross_test/i686-unknown-linux-gnu/stable	1m 35s
tests/1.64.0	3m 49s
miri	2h 31m 54s
conclusion	1s
	2h 54m 42s

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