Scaffold rewrite

[rfresh2]

Describe the pull

Makes tower mode actually work. And adds ghost blocks instead of waiting for block change packets - giving increased placing speed.

tested working on 2b2t

Additional context

@Avanatiker I know you had your own scaffold rewrite branch so if there's additional changes on your end on that feel free to edit.
I also removed my schematic placing feature as we discussed this would likely fit better into the activity system.

ToDo:

• Go down feature that listens for sneak keydown and selects player.flooredpos.down().down() and cancels the safewalk
• Fix empty hand building mentioned in line 120
• Fix illegal jump velocity
• Fix not pulling material to main hand when hotbar is empty
• Change the ScaffoldBlockSelectionMode when to be more generic
• Fix sneak on container placements