speed up 128-bit fft using faster sum, mul, and using more lanes with avx512 #93

Job	Run time
cargo-tests (ubuntu-latest)	6m 0s
cargo-tests-nightly (ubuntu-latest)	7m 25s
cargo-tests (macos-latest)	11m 17s
cargo-tests-nightly (macos-latest)	19m 17s
cargo-tests (windows-latest)	8m 37s
cargo-tests-nightly (windows-latest)	10m 49s
cargo-tests (m1mac)	1m 35s
cargo-tests-nightly (m1mac)	1m 33s
	1h 6m 33s

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