Adds a new obj_flag that prevents building on objects that shouldn't be built on.
Adds it to the stasis bed and the sleeper, as well as some machines that become undense when the doors opens (nanite chambers, DNA scanners, suit storage unit, and gulag teleporter).
If I forgot any feel free to lmk.
Fixes#58528 (Operating table + stasis bed memes)
Some objects/machines that aren't dense (or become undense in certain states) shouldn't be able to be built upon, so this flag allows for specifying that you can't build on it.
5ba06243bc