`Update` performance

Looking into the implementation of `Update`, it seems to me that the filtering of rows happens again and again for each column while this could be a one-time operation.

As a broad overview, the current situation looks like:
```kotlin
fun updateImpl() {
df.replace(columns).with { it: DataColumn -> /* filter, given entire df row and replace column */ }
}
```
while it could be
```kotlin
fun updateImpl() {
df.filter { /* Filter rows */ }.replace(columns).with { it: DataColumn -> /* replace column */ }
}
```

There is of course also a trade-off, because this doesn't work with `Update.perCol {}`, since it would supply a filtered column instead of the entire column like now. So we need to think this through thoroughly.