Nonce generating function should be abstracted over a monad

[Martoon-00]

Description

Currently, generate :: IO Nonce works only in IO.

This means, that if I have primitives containing nonce, generators for these primitives are bound to IO too. If I want to use deterministic generation in tests, I have to re-implement generation logic from scratch in pure environment.

See this module from Morley project as an example. It declares createChestAndChestKey generator in IO, and then has to re-implement it from scratch in pure way, see createChestAndChestKeyFromSeed.

So I want crypto-sodium to expose some MonadRandom, and let the generation of nonce work there.

Acceptance criteria

• That module from Morley defines only one createChestAndChestKey generator.
• This generator is easy to run both in IO and in Hedgehog tests.