feat(deps): gate blake3/p64/fractal behind hpc-extras feature (sprint A1) #201

Job	Run time
format/stable	31s
native-backend/stable	51s
Pass MSRV values to other jobs	4s
nostd/thumbv6m-none-eabi/stable	34s
cross_test/i686-unknown-linux-gnu/stable	1m 44s
cross_test/s390x-unknown-linux-gnu/stable	1m 50s
clippy/stable	42s
cargo-careful	0s
miri	0s
docs/nightly	0s
blas-msrv	1m 10s
tests/beta	1m 4s
tests/1.64.0	1m 11s
tests/stable	1m 3s
conclusion	0s
	10m 44s

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