Create a separate type for PoolDistr voting

1. Create Voting Stake Pool Distr
```haskell
data VotingStakePoolDistr = VotingStakePoolDistr
{ unPoolDistr :: !(Map (KeyHash StakePool) (CompactForm Coin))
, pdTotalStakePoolVotingAmount :: !(NonZero Coin)
}
```

1. remove `poolDistrDistrL` and `poolDistrTotalL` in favor of matching lenses for `VotingStakePoolDistr`

1. Use `VotingStakePoolDistr` in `DRepPulser`

1. Convert from PoolDistr to `VotingStakePoolDistr` on `setFreshDRepPulsingState`

1. Remove the haddock on PoolDistr
```
-- In addition to
-- the stake considered for the `individualPoolStake` Rational, we add
-- proposal-deposits to this field."
```