`array.{first,last}` `default` argument in value position

### Description

In value position, allow passing a named `default` argument to `array.first` and `array.last` that would behave like the one on `array.at`.

### Use Case

Being able to use the more readable `array.first` and `array.last` methods instead of `array.at`with `0` and `-1` when a default value is needed.