audit: replace all uses of std.time.milliTimestamp as a seed with parameterized seeds or RNGs

[InKryption]

We should replace all uses of std.time.milliTimestamp as a seed that aren't obviously at the highest level of code, with a std.Random interface parameter, or a pointer to a concrete PRNG implementation if specific random behavior is desired/required.

This would facilitate testing by making behavior deterministic, and as well allow us to more easily identify when we could use a better source of entropy than timestamps, which are a poor source.

Originally posted by @InKryption in #157 (comment)