While this isn't expected to materially improve performance, it
does get us ahash 0.8, which allows us to reduce fuzzing
randomness, making our fuzzers much happier.
Sadly, by default `ahash` no longer tries to autodetect a
randomness source, so we cannot simply rely on `hashbrown` to do
randomization for us, but rather have to also explicitly depend on
`ahash`.
Rather than using the std benchmark framework (which isn't
maintained and is unlikely to get any further maintenance), we swap
for criterion, which at least gets us a variable number of test
runs so our benchmarks don't take forever.
We also fix the RGS benchmark to pass now that the file in use is
stale compared to today's date.
