[Lens] Formula: Allow changing sorting config for last value function

[flash1293]

The last value function doesn't allow changing the sort order or the field to sort by. This makes sense for the quick function UI to make the feature easier to understand, but in the formula we could offer a way to control these settings via parameters:

• Sort ascending/descending
• Change field to sort by

[elasticmachine]

Pinging @elastic/kibana-app (Team:KibanaApp)

[markov00]

Closing this because it's not planned to be resolved in the foreseeable future. It will be tracked in our Icebox and will be re-opened if our priorities change. Feel free to re-open if you think it should be melted sooner.