Moves scripts and CI/CD to nextest #496

Job	Run time
miri	2m 54s
nostd/thumbv6m-none-eabi/stable	19s
cross_test/i686-unknown-linux-gnu/stable	2m 5s
cross_test/s390x-unknown-linux-gnu/stable	8m 28s
format/nightly	16s
docs/nightly	19s
cargo-careful	2m 7s
Pass MSRV values to other jobs	3s
clippy/stable	25s
blas-msrv	53s
tests/stable	2m 13s
tests/nightly	2m 19s
tests/beta	2m 28s
tests/1.64.0	3m 3s
conclusion	2s
clippy/stable	24s
docs/nightly	23s
format/nightly	14s
cargo-careful	1m 51s
Pass MSRV values to other jobs	2s
nostd/thumbv6m-none-eabi/stable	20s
miri	1m 52s
cross_test/s390x-unknown-linux-gnu/stable	1m 51s
cross_test/i686-unknown-linux-gnu/stable	1m 50s
blas-msrv	55s
tests/stable	1m 45s
tests/nightly	1m 45s
tests/beta	1m 36s
tests/1.64.0	1m 46s
conclusion	3s
	44m 31s

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