Moves scripts and CI/CD to nextest (#1514) #502

Job	Run time
clippy/stable	19s
Pass MSRV values to other jobs	2s
miri	10m 8s
docs/nightly	24s
cargo-careful	1m 58s
format/nightly	13s
nostd/thumbv6m-none-eabi/stable	21s
cross_test/s390x-unknown-linux-gnu/stable	8m 28s
cross_test/i686-unknown-linux-gnu/stable	2m 6s
blas-msrv	54s
tests/stable	2m 9s
tests/nightly	2m 28s
tests/beta	2m 15s
tests/1.64.0	3m 9s
conclusion	2s
	34m 56s

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