Updates to random number generation APIs
Updates based on discussions about random number generation.
- Add comment on `RandomSource::fill_bytes` about multiple calls, to allow
efficient implementations for random sources that generate a word at a time.
- Drop the `Random` trait in favor of `Distribution<T>`, which will let people
make calls like random(1..=6), and which allows for future expansion to
non-uniform distributions, as well as floating-point. (For now, this is only
implemented for `RangeFull`, to get the interface in place. Subsequent PRs
will implement it for other range types.)
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