Dont leave pillars/bridges behind (backfill with air)

## Describe your suggestion
An option to auto delete pillars as you build them.

## Settings
toggle for both pillars and bridges

## Context
When clearing an area or replacing specific items with air baritone builds pillars and bridges with throwawayblocks to reach higher blocks. However, it often then just leaves those pillars and bridges making it worse than it began.
My suggestion for an easy fix is to have an option for baritone to delete these as it builds them. For example, as its pillaring, it makes a pillar of 2 dirt, it then looks down and deletes the dirt below the one you're standing on. It obviously repeats this step.

Essentially it is doing backfill with air for bridges and pillars so as to not leave ugly stacks of dirt floating all over in areas that were just cleared.

## Final checklist
- [x] I know how to properly use check boxes
- [x] I have not used any OwO's or UwU's in this issue.