Switch to using `Data.Vector.Strict` with `VMap`

Currently, `Data.Vector (Vector)` is used for boxed storage in `VMap`, for example in `Snapshots`:

```
data SnapShot = SnapShot
{
...
, ssDelegations :: VMap VB VB (Credential Staking) (KeyHash StakePool)
, ssPoolParams :: VMap VB VB (KeyHash StakePool) StakePoolParams
, ssStakePoolsSnapShot :: !(VMap VB VB (KeyHash StakePool) StakePoolSnapShot)
}
```

Once we switch to `vector-0.13.2.0` , we can use `Data.Vector.Strict` wherever we want to make sure there are no thunks.

The `NoThunks` instance for `Data.Vector.Strict` has already been implemented in this PR: https://github.com/IntersectMBO/cardano-ledger/pull/5545.

With the switch, we should also implement the now commented out functions: `mapValsKVVector` and `mapWithKeyKVVector` in `Data.VMap.KVVector` and then switch to them in the respective function `map` and `mapWithKey` in the `Data.VMap` module.

Start in Data.VMap.KVVector by reading the commented-out mapValsKVVector and mapWithKeyKVVector functions, then inspect the corresponding map and mapWithKey functions in Data.VMap. Use the vector-0.13.2.0 requirement and PR 5545 as context; done means VMap uses Data.Vector.Strict for the relevant boxed storage and those functions are implemented and selected.

Written by the indexing model from the issue text.