Rewrite GHASH to use 128-bit multiplication over non-reversed
integers, and up to 8 blocks aggregated reduction.
lib/std/crypto/benchmark.zig results:
Xeon E5:
Before: 1604 MiB/s
After: 4005 MiB/s
Apple M1:
Before: 2769 MiB/s
After: 6014 MiB/s
This also makes AES-GCM faster by the way.