fix: remove timex package

[nrwiersma]

Goal of this PR

This removes the use of github.com/hamba/timex as it no longer has a speed advantage.

name         old time/op    new time/op    delta
WithStats-8     164ns ±20%     158ns ±14%   ~     (p=0.529 n=10+10)

name         old alloc/op   new alloc/op   delta
WithStats-8     41.0B ± 0%     41.0B ± 0%   ~     (all equal)

name         old allocs/op  new allocs/op  delta
WithStats-8      4.00 ± 0%      4.00 ± 0%   ~     (all equal)

How did I test it?