CoinsRegistry: CoinsByOutPoint -> CoinsByPrevOuts

[kiminuo]

CoinsByOutPoint (Dictionary<OutPoint, HashSet<SmartCoin>>) is not good especially because we have OutpointCoinCache (Dictionary<OutPoint, SmartCoin>)

[turbolay]

Just a quick note, it's not really by PrevOut, as it's by Inputs' PrevOuts. So the name might suggest that it's the same as the CoinsByOutPoint cache.
In fact, it should even be grouped by transactions, as the values are grouped by transaction anyway (This was the idea of #11516), but anyway, this name is better. The previously introduced comment is a great help

[adamPetho]

LGTM

[kiminuo]

Just a quick note, it's not really by PrevOut, as it's by Inputs' PrevOuts. So the name might suggest that it's the same as the CoinsByOutPoint cache.
In fact, it should even be grouped by transactions, as the values are grouped by transaction anyway (This was the idea of #11516), but anyway, this name is better. The previously introduced comment is a great help

I agree. I'll merge this but feel free to suggest a better name. I'm playing with Adam's PR to remove this altogether but I figured it's better to rename it anyway because the name is confusing to me. The new one is at least less confusing.