Consolidate Abstract Info/Lightweight Buildable info

[budak7273]

Move info from https://docs.ficsit.app/satisfactory-modding/latest/Development/UpdatingFromSml37.html#_lightweight_buildable_system into the Abstract Instance page

Mention that the lightweight system means that since they implemented the lightweight system, foundations, walls, etc. no longer increase the UObject count
https://discord.com/channels/555424930502541343/555505343031934979/1382636751687778378