AI pickup changes (#1811)

* AI pickup changes

Eating and drinking isn't spammed anymore.
AI can do InRangeUnobstructed checks for item pickups.
AI can open drink cans.

AI littering to be coded.

* #nullable enable

* github's nullable fails are actively shortening my lifespan

* Use a const instead

So it's easier to find given the performance implications.

Co-authored-by: Metal Gear Sloth <metalgearsloth@gmail.com>

Content.Server/AI/Operators/Sequences/GoPickupEntitySequence.cs

@@ -11,7 +11,7 @@ namespace Content.Server.AI.Operators.Sequences
         {
             Sequence = new Queue<AiOperator>(new AiOperator[]
             {
-                new MoveToEntityOperator(owner, target),
+                new MoveToEntityOperator(owner, target, requiresInRangeUnobstructed: true),
                 new OpenStorageOperator(owner, target),
                 new PickupEntityOperator(owner, target),
             });