track go/issues/66821: crypto/rand: throw on errors

[komuw]

I'm proposing we make crypto/rand throw (irrecoverably crash the program) if an error occurs, 
and document that the error return values of crypto/rand.Read and crypto/rand.Reader.Read are always nil.
This will also allow introducing new APIs like a hypothetical String(charset string) string (not part of this proposal) 
without an error return, making them more usable and appealing.

https://github.com/golang/go/issues/66821

This would probably enable us to use crypto/rand in https://github.com/komuw/ong/blob/main/id/id.go