I keep wanting to name it GenerateEntropy, but golang convention tells you not to worry about the 'generate' prefix. We could call it `NewEntropy()` if that is less confusing. Or perhaps `NewEntropyStage2()`

Btw I switched things from `Stage1Entropy` to `EntropyStage1` because it made more sense to me to have the important part first, as it's not the only piece that exists in 2 stages (the file proof also has 2 stages)